The past two decades have witnessed rapid and remarkable technical improvement of multidetector computed tomography (CT) in both image quality and diagnostic accuracy. These improvements include higher temporal resolution, high-definition and wider detectors, the introduction of dual-source and dual-energy scanners, and advanced postprocessing. Current new generation multidetector row (≥64 slices) CT systems allow an accurate and reliable assessment of both coronary epicardial stenosis and myocardial CT perfusion (CTP) imaging at rest and during pharmacologic stress in the same examination. This novel application makes CT the unique noninvasive “one-stop-shop” method for a comprehensive assessment of both anatomical coronary atherosclerosis and its physiological consequences. Myocardial CTP imaging can be performed with different approaches such as static arterial first-pass imaging, and dynamic CTP imaging, with their own advantages and disadvantages. Static CTP can be performed using single-energy or dual-energy CT, employing qualitative or semiquantitative analysis. In addition, dynamic CTP can obtain quantitative data of myocardial blood flow and coronary flow reserve. The purpose of this review was to summarize all available evidence about the emerging role of myocardial CTP to identify ischemia-associated lesions, focusing on technical considerations, clinical applications, strengths, limitations, and the more promising future fields of interest in the broad spectra of ischemic heart disease. Since the clinical introduction of multidetector computed tomography (CT) in the late 1990s , coronarIn consideration of its high sensitivity and negative predictive value (≥95%) for the detection of significant coronary stenosis , coronarThe EVINCI  study, a prospective multicenter European comparative effectiveness trial, has demonstrated that comprehensive assessment of anatomic CAD by CTA had a sensitivity of 91% and specificity of 92%, which were higher than functional test including myocardial perfusion imaging by either single photon emission computed tomography (SPECT) or positron emission tomography (PET) and ventricular wall motion imaging by either stress echocardiography or magnetic resonance imaging (MRI) . HoweverThe effects on clinical decision-making due to incorporation of CTA in the chest pain care pathway, jointly with its safety, are demonstrated in the SCOT-HEART  and in tCoronary CTA has also a prognostic value providing information on the total plaque burden, with a better outcome when there is no evidence of CAD and a worse prognosis in case of detection of coronary atherosclerosis, depending on its severity and extension –15.Moreover, it has the ability to detect nonobstructive non-flow-limiting CAD, helping to identify patients at risk of future cardiac events with more precision than functional testing .The actual limit of coronary CTA is the impossibility to assess the functional significance of coronary stenosis related to its moderate positive predictive value (about 50%) in detecting inducible myocardial ischemia –19.Physiological evaluation needs to be improved, because it influences the outcome of CAD more than its anatomical detection. In fact, studies using fractional flow reserve (FFR) have demonstrated that ischemia-guided coronary revascularization, especially percutaneous coronary intervention (PCI), is superior to angiography-guided strategy –23.In absence of myocardial ischemia, revascularization is associated with no symptomatic or prognostic benefit for patients, while it is effective in patients with moderate to severe ischemia  .The evidence of coronary stenosis, especially for luminal narrowing of 30-70%, is not predictive of inducible ischemia. Further functional test, such as SPECT, stress echocardiography, or stress perfusion MRI are needed to guide revascularization indication .Furthermore, a subanalysis of the EVINCI study has shown that, in patients at intermediate risk of CAD, hybrid imaging with CTA and SPECT allows noninvasive colocalization of myocardial perfusion defects and subtending coronary arteries, impacting clinical decision-making in almost one in every five subjects .In the last decades, we observed a rapid technological improvement, which led to a notable reduction of the scan time, motion artifacts, use of contrast agent, and radiation dose exposure, while yielding, at the same time, higher spatial and temporal resolution –27 whichThe purpose of this review was to summarize all available evidence about the emerging role of myocardial CTP in the assessment of the hemodynamic impact of coronary lesions, focusing on technical considerations, clinical applications, strengths, limitations, and the more promising future field of interest in the broad spectra of ischemic heart disease.In the classic ischemic cascade, perfusion abnormalities are the first to occur, before metabolic alterations, wall motion abnormalities, ECG changes, and symptoms.Stress tests evaluating myocardial perfusion have a higher sensitivity in detecting flow-limiting stenosis compared with other imaging modalities based on the induction of stress-induced wall motion abnormalities or ECG changes .Gould in 1974 was the first to investigate the relationship between luminal artery narrowing and the maximal hyperemic response .Thanks to coronary autoregulation, involving myogenic and metabolic mechanism, myocardial perfusion at rest is normal until the luminal diameter narrowing of a coronary artery exceeds 85-90%.However, in presence of coronary stenosis greater than 45% maximal coronary hyperemia induced by coronary arteriolar vasodilator leads to a progressive decrease in the hyperemic response .In this situation, exercise or pharmacological vasodilation of subepicardial resistance vessels results in a reduction in distal coronary pressure that redistributes flow away from the subendocardium, leading to a “transmural steal” phenomenon .Pharmacological stress agents are used to induce the hyperemic response in patients who cannot afford exercise test, that is, the preferred method to induce myocardial hyperemia.For stress CTP, the most used substances are adenosine and dipyridamole that lead to arteriolar vasodilation by both direct and endothelium-mediated mechanisms through stimulation of A2A receptors in the microvasculature. In the absence of microcirculatory dysfunction, the vasodilatory response is associated with a 3.5- to 4-fold increase in myocardial blood flow .Two intravenous (IV) lines are essential in CTP imaging for injection of the contrast media and of the vasodilator agent, respectively.Adenosine is a powerful, endogenous molecule with a nonselective activation of four distinct subtypes  receptors. Its infusion rate is 140 mcg/kg/min for 3 to 5 minutes with an infusion pump. Side effects could be AV block, peripheral vasodilation, and bronchospasm, but the most common are flushing, chest pain, dyspnea, dizziness, or nausea. Compared to dipyridamole, adenosine has a more rapid onset of action and a shorter half-life of 30 s; therefore most side effects resolve in a few seconds after discontinuation of the adenosine infusion.Dipyridamole increase intracellular and interstitial concentration of adenosine, indirectly leading to coronary arteriolar vasodilatation, and it does not require an IV pump for infusion as it can be applied manually at a slow rate in a dose of 0.56 mg/kg to 0.84 mg/kg over a 4- to 6-minute period. Due to its longer half-life of approximately 30 minutes, dipyridamole-stress patients may require administration of aminophylline (slow intravenous injection of 50 mg to 250 mg) for reversal of persistent symptoms , 34, 37.Recently, a new agent named regadenoson, an A2A selective agonist administered via a prefilled syringe in a single dose (400 mg) over 10 seconds, has been introduced as a pharmacologic stress vasodilator. It has a safer side effect profile in comparison to adenosine and dipyridamole, especially for patients with asthma or severe chronic obstructive pulmonary disease but it is limited by its cost and it is not widely available.Regadenoson has been shown to be accurate for the detection of obstructive CAD in nuclear perfusion imaging, stress echocardiography, and, more recently, stress CTP studies , 38, eveβ1-adrenergic receptors agonist, with mild effect on α1- and β2-receptors [μg/kg/min), dobutamine improves myocardial contractility and induces coronary vasodilation; at higher doses (20-40 μg/kg/min), it causes systematic vasodilation and serves as a positive chronotrope [Of note, the myocardial perfusion can be evaluated by dobutamine as well . The syneceptors . At low onotrope . At thesonotrope . In the onotrope , 40. Cononotrope , 40.Dobutamine is not the preferred pharmacological stressor in CTP imaging. However, as described by a recent case report, it may have a value to risk stratify patients with an anomalous coronary artery, since vasodilator stress imaging might not be sufficiently sensitive to identify dynamic coronary compression .The protocol of CTP imaging includes evaluation of myocardial perfusion during both rest (baseline) and stress (hyperemia) conditions and it is similar to other noninvasive imaging techniques such as stress cardiac MRI and nuclear imaging .CTP analysis is performed after administration of iodinated contrast through an antecubital IV access by imaging the left ventricular (LV) myocardium during the first pass of the contrast bolus. Iodinated contrast attenuates X-rays directly proportionally to iodine content in tissue; thus myocardial perfusion defects can be directly visualized as hypoattenuated or nonenhancing regions.Imaging during the early portion of first-pass circulation is critical, since after about 1 min a rapid wash-out of contrast agent due to diffusion to the extravascular space is expected .Contrast injection needs, at high flow rate, at least 5 mL/s for optimizing the strength of enhancement in the first-pass arterial phase .There are two protocols mostly used, named according to sequence of scan acquisitions: rest/stress or stress/rest. An interval of 10-15 minutes between the two sequences provides optimal contrast wash-out , 34.The rest/stress protocol uses the ability of coronary CTA to rule out obstructive CAD. CTP is performed only in the presence of anatomically defined CAD of intermediate or obstructive degree, avoiding further radiation and iodinated contrast exposure in absence of coronary artery stenosis. This protocol is limited by the cross-contamination of contrast in the stress phase and beta-blocker administrated before the rest acquisition, leading to underestimation of myocardial ischemia.The stress/rest protocol avoiding the risk of residual contrast media derived from the rest phase that may confound perfusion defects is optimized for the detection of myocardial ischemia.The contrast media contamination of the rest phase may decrease sensitivity for infarction , 34.Definitely, the best approach should be tailored on the patient's risk profile, reserving the rest/stress CTP for patients with low-to-intermediate pretest probability of CAD and stress/rest CTP for patients with high pretest probability of ischemia-associated lesions .Myocardial CTP imaging can be performed with different approaches such as static arterial first-pass imaging and dynamic time-resolved CTP imaging, with their own advantages and disadvantages.The static CTP imaging is based on acquisition of one single phase during the first-pass of the contrast agent. Certain technical challenges involving scan timing relative to maximum contrast enhancement and optimal contrast material delivery must be met .Generally, rest myocardial CTP imaging is derived from the coronary CTA examination.ECG-gating of coronary CTA or CTP can be retrospective (with prospective tube current modulation) , 43 but Prospectively ECG-triggered high-pitch spiral acquisition implemented with the second-generation 128-slice dual-source CT (DSCT) scanner allows the acquisition of the volumetric data of the heart in a single cardiac cycle with radiation exposure as low as 1 mSv , 46.Visual qualitative assessment is the analyzing method of static CTP. Thick multiplanar reconstructions of approximately 5 mm to 8 mm are usually recommended for myocardial perfusion analysis to improve the contrast-to-noise ratio.Myocardial contrast enhancement increases proportionally with iodine concentration, so perfusion defects appear as hypodense region with subendocardial or transmural distribution with respect to the normal myocardium.An integrated review of stress and rest images is important to characterize not only ischemic from nonischemic myocardium, but also viable versus nonviable myocardium by differentiating between fixed and inducible perfusion abnormalities .Hypoperfusion in stress with normal perfusion in rest underlines ischemia, whereas hypoperfusion in stress that persists with same extension in rest is indicative of necrosis . FurtherThe final step to the analysis of a CTA/CTP study is the match of perfusion defects with the anatomic localization of coronary epicardial stenosis, Automated software application provides analysis of semiquantitative metrics such as the transmural perfusion ratio (TPR), determined as the ratio of subendocardial to mean subepicardial contrast attenuation, which has been already initially validated for MRI perfusion. However, the accuracy of TPR may be significantly affected by motion and beam-hardening artifacts or by a thinning myocardial wall in the context of prior infarction .In conclusion, the patient specific ischemic burden may be determined in terms of volume of CT perfusion defect or percentage of ischemic myocardium relative to global myocardial volume .Dual-energy CT (DECT) myocardial perfusion imaging technology provides additional information about myocardial tissue composition compared with conventional single-energy computed tomography (SECT). Moreover, DECT improves limitations that are commonly present in SECT such as beam-hardening artifacts and blooming artifacts by using monochromatic image reconstruction .Based on the specific attenuation spectral characteristics of the different tissues when exposed to two different photon energy levels, DECT enables distinguishing the features of the tissue and evaluating the myocardial blood supply by mapping iodine distribution within the myocardium .Iodine map provides a measure of per-voxel iodine myocardial concentration expressed in mg/mL, which improves accuracy when compared to standard visual analysis , 49, 51,Different vendor-specific CT technologies have been developed to perform dual-energy acquisitions. Dual X-ray source system  is the most commonly used technology: there are two independent tubes paired with two detectors that simultaneously emit high (140-150 kV) and low (80-90-100 kV) energy levels .A second modality is based on single-source CT with rapid (about 0.25 ms) switching of tube voltage between 80 and 140 kV either in a single gantry rotation  or in sequential rotations  .The dual-layer (“sandwich”) detector  is an alternative approach made of two different materials able to differentiate between low and high energy photons, with the source operating at constant tube voltage; however this system is not yet available in routine clinical practice .Finally, the use of second- or third- generation DSCT scanners with high temporal resolution  could help discriminate between motion artifacts due to irregular or high heart rates and true perfusion defects, avoiding false positive findings .The only CT based technology that permits absolute quantification of myocardial perfusion is dynamic CTP imaging. It is based on repeated acquisition of the myocardial tissue during the first-pass contrast uptake to create time-attenuation curves (TACs) for the region of interest (ROI) , providiHemodynamic parameters, such as the myocardial blood flow (MBF), MBF ratio, and myocardial blood volume (MBV), and semiquantitative parameters such as the up-slope, peak enhancement, time to peak (TTP), tissue transit time (TTT), and area under the curve (AUC) are derived by dedicated algorithms of these TACs  , 55.Recently, the introduction of semiautomated three-dimensional software allowed a substantial reduction of the postprocessing phase, making the dynamic CTP more suited to routine clinical practice , Figure Whole-heart spatial coverage with appropriate temporal resolution is crucial to obtain multiple consecutive images at high heart rates .Dynamic datasets acquisition is currently performed with two different approaches. The first one provides the use of single-tube multidetector CT scanners with 256 or 320 detector rows, which cover the whole cardiac volume while the table is stationary . An alternative approach is second- and third-generation DSCT scanners, able to perform dynamic CTP imaging: by moving the scanner table back and forth (“shuttle mode”) between two scanning positions; it is possible to achieve a coverage of 73 or 105 mm, respectively, for the second- and third-generation DSCT scanners .In both cases, image acquisition is performed during the systolic phase of the cardiac cycle when apical-basal length is shorter and myocardial wall is at maximal thickness.Systolic phase length is relatively constant (about 200 ms) even when heart rate is high and irregular, so, images acquired in systole are less vitiated to beam-hardening artifacts because the amount of contrast medium needed for this phase is lower  .The obstacles to the clinical routine application of dynamic CTP are high radiation exposure, the relatively long breath-hold (approximately 30 sec) necessary for whole cardiac volume scanning, and spatial misalignment from two separated table positions when shuttle mode is used .The use of motion correction and beam-hardening correction algorithms could minimize artifacts, improving image quality and diagnostic accuracy .Advantages and disadvantages of static and dynamic CTP imaging are summarized in Many clinical studies and the first prospective multicenter trials have established the clinical feasibility and the diagnostic accuracy of static and dynamic CTP compared to SPECT, stress MRI, and/or invasive coronary angiography with and without fractional flow reserve (FFR), Tables 2A recent meta-analysis including 1188 patients in 19 studies showed that static CTP imaging in case of suspicion of known CAD, had a good agreement with SPECT and stress MRI perfusion with a sensitivity and specificity of 85% and 81%, respectively. When ICA was used as reference standard alone or in combination with SPECT or FFR, combined coronary CTA and CTP compared to coronary CTA alone significantly increased the specificity from 62% to 84% without significant decrease in sensitivity .Similar results were obtained in a meta-analysis of Takx et al.  evaluatiA prospective multicenter international trial, the CORE 320 study (n=381), has confirmed that static CTP imaging has a higher accuracy in comparison with SPECT in terms of significant CAD (≥ 50%) detection, using as reference ICA . The betThe increased sensitivity of CTP also derives from the more favorable extraction characteristics of iodinated contrast material allowing for a linear relationship between CT-derived metrics and myocardial blood flow. Conversely, Technetium-based tracers show a nonlinear net-tracer uptake in particular in the higher coronary flow range, causing the well-known-roll-off phenomenon .The CORE 320 studies have also proved that the specificity and overall accuracy of coronary CTA in detecting significant CAD (≥50%) defined by ICA and SPECT are significantly increased by the addition of CTP at both the patient and vessel levels , 63. ThiAnother recent randomized, multicenter, multivendor CTP study with regadenoson (n=110) by Cury et al. has shown that regadenoson-CTP imaging improved the diagnostic accuracy of coronary CTA from 69% to 85%, in particular by reducing the rate of false positive CTA results .Moreover, CTP showed a high sensitivity and specificity of 90% and 84%, respectively, for the detection of myocardial ischemia as defined by a reversible perfusion defect in ≥ 2 myocardial segments on SPECT, with an agreement rate of 87% .A considerable increase in diagnostic performance has also been largely proved when dual-energy myocardial CTP was coupled to coronary CTA, especially in terms of specificity, According to Meinel et al. the rest-stress protocol should be the first choice for evaluation of the myocardial blood supply in dual-energy CTP, with a sensitivity of 99%, specificity of 97%, positive predictive value (PPV) of 92%, and NPV of 100% using SPECT as reference of standard .The DECIDE-Gold, an ongoing prospective multicenter study, will define the diagnostic accuracy of dual-energy to detect hemodynamic significant CAD, comparing it to fractional flow reserve (FFR) as a reference standard .The available published data seem to suggest that static dual-energy and quantitative dynamic CTP imaging have a higher sensitivity, with respect to standard static monoenergetic CTP , 53, TabStress dynamic myocardial CTP has been initially studied in preclinical trials demonstrating a good correlation of CT-derived perfusion values with microsphere derived MBF data, histopathology, and invasive measurements of coronary blood flow and FFR, It is important to note that, as reported by a recent large animal study, dynamic CTP has a superior discriminatory power in detecting myocardial ischemia than static first-pass CTP, using fluorescent microspheres as a reference standard for MBF , 84. A sClinical researches have demonstrated that dynamic stress CTP may improve the PPV and specificity of coronary CTA alone , 78, espThis modality also enables the quantification of the absolute value of coronary flow reserve (CFR) calculated as the ratio of hyperemic to baseline MBF with a high degree of correlation to SPECT , 54.Moreover, dynamic CTP is useful in the global quantitative evaluation of left ventricular myocardial perfusion, especially in case of balanced ischemia caused by multivessel CAD .According to quantitative PET and CTP studies, the relative MBF (an absolute MBF-to-remote MBF ratio) leads to better detection of hemodynamically significant coronary stenosis than does the absolute MBF derived from dynamic CTP imaging, probably reducing the impact of microvascular resistance on myocardial perfusion –89.Semiquantitative parameters such as the TPR and myocardial reserve index (defined as the ratio of hyperemic and resting blood flow) have been suggested for static and dynamic myocardial CTP; however, they have a lower diagnostic accuracy than qualitative analysis by standard visual assessment , 57, 90.The CATCH-2 (CArdiac cT in the treatment of acute CHest pain 2), a prospective randomized controlled multicenter study published in 2017, has showed the usefulness of myocardial CTP assessment in addition to CTA, in patients with recent acute-onset chest pain when acute coronary syndrome had been excluded, and who had a clinical indication for outpatient noninvasive testing . CouplinFinally, as proved by a CATCH-trial substudy, myocardial CTP parameters predict mid-term clinical outcome in patients with recent acute-onset chest pain independently of the pretest probability of obstructive CAD . InteresDuring the last years, CT scanners with higher spatial resolution (approximately 1/3 of millimeter), temporal resolution (up to 66 ms), and wider detector array (up to 320-detector row) were developed, with a substantial improvement in CT performance and reduction of radiation exposure . FurtherConsequently, the contemporary estimated effective dose of coronary CTA and myocardial static CTP imaging will typically range between approximately 1.5 and 5.0 mSv, with an effective dose even to sub-millisievert levels for some exams , 93.However, numerous factors may influence the radiation dose, such as patient's characteristics , the type of CT equipment available, and the CT protocols used, which has to be tailored to the patient. Despite these promising innovations, the relatively high radiation exposure during dynamic CTP acquisitions remains a problem to be solved since it acquires a series of multiple low-dose acquisitions for the generation of TACs. Recent data have demonstrated that the average radiation exposure of dynamic CTP imaging is greatly depending on protocol optimization with an average value of 9.23 mSv (versus 5.93 mSv for static CTP) , which iHowever, Hubbard et al. validated a low-dose dynamic CTP technique based on a first-pass analysis model by using only 2 volume scans as compared with standard protocol based on multiple acquisitions in an animal model, showing good correlation with invasive FFR at different stenosis severity reaching overall effective radiation doses of 2.64 mSv .So current efforts are directed towards further reducing radiation exposure while maintaining a high diagnostic performance. In this regard, the use of recent technical innovations, including the low voltages (70 kV to 80 kV) acquisition, automated tube current modulation, and iterative reconstruction, seems to be able to achieve this ambitious goal .Many noninvasive techniques can perform an evaluation of myocardial perfusion, including SPECT, stress MRI, stress echocardiography, and positron emission tomography (PET) . NuclearPET is the gold standard for absolute quantification of myocardial perfusion particularly when 13N-ammonia is used and may be superior to SPECT in spatial resolution, image quality, and diagnostic accuracy . HoweverThese observations have fueled the pursuit of hybrid imaging strategies in which radionuclide myocardial perfusion imaging is combined with coronary CTA. While promising, this approach has some important disadvantages including higher radiation doses and elevated costs .Moreover, important SPECT limitations are the underestimation of the true extent of disease in patients with multivessel CAD and the photon attenuation artifacts typically due to breasts in women and diaphragm in men .MRI is the most versatile imaging modality: it can be used for morphology, function, viability, and quantitative myocardial perfusion assessment . Stress Stress echocardiography is a well-established, real-time imaging modality with advantages including lack of radiation exposure, versatility, and affordability. Dobutamine stress echocardiography could provide information about ischemic abnormal ventricular wall motion but this modality is lower than dobutamine stress MRI in terms of specificity (87.5% versus 72.9%), negative predictive value (80.8% versus 67.3%), and overall diagnostic accuracy (80.4% versus 72%) .The introduction of ultrasound contrast agents (microbubbles) has optimized the detection of RWMA and has enabled simultaneous assessment of left ventricular perfusion and viability, improving the sensitivity of the technique .According to a large multicenter prospective trial, myocardial contrast echocardiography (MCE) has higher sensitivity but lower specificity compared to SPECT for CAD evaluation . The supAlthough functional information provided by any of these techniques is well-validated and extremely useful, none of them provide a comprehensive anatomical-functional evaluation within the same study. Currently, myocardial CTP imaging is the only noninvasive modality that allows quantifying coronary stenosis and determining its functional relevance, rendering it a potential “one-stop-shop” method for the diagnosis and global management of patients with ischemic heart disease .Moreover, the imaging matrix of 512 × 512 pixels with an isotropic high spatial resolution (approximately 0.3 mm) of CTP is superior to nuclear imaging and enables evaluation of transmural differences in myocardial blood flow .Moreover, CTP imaging using the iodinated contrast agent does not suffer of the nonlinear relationship between myocardial signal intensity and gadolinium contrast concentration, which might affect the accuracy of quantitative analysis of MBF in MRI perfusion imaging .Finally, the wide availability of modern CT scanners makes CTP more accessible compared with other noninvasive tools, such as MRI or PET imaging .Advantages and disadvantages of functional imaging with echo, SPECT, MRI, and CTP imaging are reported in CT) using computational fluid dynamics has been clinically validated [Recently, a new technique to allow for noninvasive calculation of FFR based on conventional coronary CTA data  will compare the diagnostic performance of an FFRCT-guided strategy to stress CTP for the detection of functionally significant CAD, using invasive FFR as the reference standard .The current evidence suggests that myocardial CTP imaging improves diagnostic accuracy of coronary CTA alone mainly by reducing the number of false positive findings, even when compared with invasive FFR.With respect to this issue, an integration of both anatomical and physiological assessment of CAD may be a more robust “gatekeeper” to ICA by increasing the diagnostic accuracy while maintaining higher sensitivity compared to anatomical assessment alone. This may be particularly useful in difficult-to-interpret situations, such as in patients with coronary stents and heavily calcified coronary arteries in which blooming artifacts can hamper lumen visualization and correct stenosis measurements. Accordingly, recent studies have shown that stress CTP improves diagnostic performance in patients with a high Agatston calcium score  or coronThe utility of hemodynamic assessment by the integration of CTP and coronary CTA may have a potential role in stratifying cardiovascular risk and in the decision-making for the optimal medical intervention, although this potential role warrants further investigation.Furthermore, in line with PET imaging, dynamic CTP imaging offers the ability to obtain quantitative data of hemodynamic parameters (such as MBF and MBV) and the assessment of absolute CFR. The combination of coronary CTA and dynamic myocardial CTP makes CT a very promising technique to evaluate patients with microvascular dysfunction because it not only reveals the absence of demonstrable obstructive CAD but also provides data about CFR, the current gold standard for clinically assessing microvascular function.Quantification of hemodynamic parameters may be particularly useful for evaluation of specific patient population, such as patients with multivessel CAD, extensive nonobstructive CAD, hypertension, and diabetes mellitus .When global myocardial ischemia exists due to multivessel CAD, it may be difficult to achieve an accurate diagnosis with the qualitative analysis method by static CTP. Conversely, MBF analysis may be able to identify multivessel disease and predict the extent of ischemia more accurately than static CTP imaging , 53.The ability to quantify absolute MBF with dynamic stress CTP imaging permits identification of patients in whom the relative regional distribution of contrast agent may appear normal because of a balanced reduction of blood flow. Moreover, in patients with diffuse nonobstructive epicardial disease but no significant stenosis, the combination of plaque analysis by coronary CTA and CFR assessment derived by stress/rest dynamic CTP imaging may be helpful in identifying hemodynamic relevant coronary plaques, although not yet obstructive, and to avoid ascribing patient's symptoms to microvascular disease . In factFurthermore, MBF analysis might also be advantageous in monitoring disease progression or perfusion changes in response to therapy such as for PET and MRI imaging , 115, alHowever, important considerations have to be highlighted when interpreting quantitative measurements of dynamic CTP. A substantial underestimation of absolute MBF from dynamic CTP has been reported, with a significant influence of CT-derived MBF by temporal sampling rate , 117. ThFinally, it is well-known that all iodinated contrast agents have an immediate and direct vasodilatory effect . All theMoreover, the reported optimal MBF cutoff values for the differentiation of normal and ischemic myocardium varied considerably between dynamic CTP studies, ranging from 75 mL/100 mL/min to 103.1 mL/100 mL/min with a dual-source CT scanner and as high as 164 mL/100 mL/min using a 256-slices CT scanner , 34. ThiMoreover, numerous individual factors such as age, gender, race, BMI, presence and severity of CAD, the status of the microvasculature, individual adaptive vasodilator responsiveness, and/or the presence of collateral flow may affect MBF , 87, 118Accordingly, considerable regional heterogeneity of the myocardial perfusion across coronary territories has been demonstrated in healthy and low-risk subjects , 119.Large inter- and intraindividual differences in MBF distribution are already known from PET and MRI studies , 34. TheHowever, a major limit of dynamic CTP is the higher dose profile respect to static CTP due to the time-resolved acquisition of multiple phases.Furthermore, CTP imaging may be affected by several artifacts, such as partial volume, beam hardening, breathing, and motion artifacts. In particular, the patient's breathing motion poses a major challenge for dynamic CTP, which requires a long acquisition time of approximately 30 s. Furthermore, the sequence “shuttle mode” implemented with the second-generation dual-source CT scanner to dynamically cover the entire left ventricle myocardium may be a source of motion artifact influencing the estimation of MBF derived from the TACs. Beam-hardening artifacts arise from the polychromatic nature of the X-rays in the CT acquisitions and the presence of high-density iodine contrast agent in the heart chambers, which results in a hypoattenuated shadowing artifact . Areas aFurthermore, some of these artifacts may be partially attenuated by well-validated beam hardening and motion correction algorithms implemented with latest CT scanner technology , 34.Moreover, in most of the CTP studies, anti-ischemic drugs such as beta-blockers have not been withheld prior to stress testing; this may negatively affect the accuracy of CTP by decreasing the severity and the extent of myocardial perfusion defects. However, it is expected that the diagnostic performance of CTP imaging performed in patients without background medications could be even higher than reported.Finally, other limits are the broad spectrum of clinical characteristics of the studied populations and the difficult to standardize the CTP imaging due to the heterogeneity of scanner manufacturers, acquisition protocols, stress protocols, image analysis algorithms, and postprocessing parameters.In addition, no large-scale multicenter studies have demonstrated the clinical value of CTP imaging. Further researches with larger sample size and improved standardization of CTP imaging technique are warranted.Current evidence suggests that adding CTP imaging is a safe and powerful tool to improve the accuracy and the positive predictive value of coronary CTA alone because it not only provides anatomic information concerning luminal stenosis, plaque morphology, and total plaque burden but also provides data on myocardial tissue hemodynamics.Different acquisition protocols for CTP imaging are available, which can assess myocardial perfusion in a qualitative, semiquantitative, or quantitative manner, with their own advantages and disadvantages.In conclusion, coronary CTA combined with myocardial CTP imaging hold immense potential to evaluate almost every aspect of the broad spectra of ischemic heart disease with the possibility of guiding treatment decisions for a patient on an individual basis. Further researches with larger sample size should be designed and implemented to decide whether to adopt this new diagnostic modality in a routine clinical setting.Finally, prognostic studies are needed to assess if this combined approach will likely have substantial impact on treatment costs, patient management, and outcome. The time to challenge this hypothesis with randomized prospective trials has come.


Brain tumors are among the deadliest malignancies. The brain tumor microenvironment (TME) hosts a unique collection of cells, soluble factors, and extracellular matrix components that regulate disease evolution of both primary and metastatic brain malignancies. It is established that macrophages and other myeloid cells are abundant in the brain TME and strongly correlate with aggressive phenotypes and distinct genetic signatures, while lymphoid cells are less frequent but are now known to have a pronounced effect on disease progression. Different types of brain tumors vary widely in their microenvironmental contexture, and the proportion of various stromal components impacts tumor biology. Indeed, emerging evidence suggests an intimate link between the molecular signature of tumor cells and the composition of the TME, shedding light on the mechanisms which underlie microenvironmental heterogeneity in brain cancer. In this review, we discuss the association between TME composition and the diverse molecular profiles of primary gliomas and brain metastases. We also discuss the implications of these associations on the efficacy of immunotherapy in brain malignancies. An appreciation for the causes and functional consequences of microenvironmental heterogeneity in brain cancer will be of crucial importance to the rational design of microenvironment-targeted therapies for these deadly diseases. The clinical management of brain tumors remains a significant challenge, as surgery and standard of care (SOC) cytotoxic therapies (including radiation and chemotherapy) often offer minimal survival benefit. The brain tumor microenvironment (TME) is a major component of brain malignancies and is a prominent regulator of disease progression and overall survival. As such, the TME compartment may host new therapeutic opportunities that could improve outcomes for brain tumor patients. Under normal physiologic conditions, the brain hosts a generally immunosuppressive milieu that protects the delicate and non-regenerative neural tissue from inflammatory insult. This is in part regulated by the blood-brain barrier (BBB), a selectively permeable barrier formed by endothelial cells, pericytes, and astrocytes , 2, whicThe brain is largely populated with unique cells that perform tissue-specific functions such as neurons, astrocytes, oligodendrocytes, and other glial cells. Moreover, cellular populations which also reside in other tissues, such as macrophages and endothelial cells, are endowed with distinct phenotypes within this vital organ –10. AddiDuring malignancy, the brain TME is co-opted to support the growth of cancer cells and shield them from immune destruction. In this review, we discuss variations in the TME of brain cancers as a function of their molecular profile . The wor6-methylguanine-DNA-methyltransferase (MGMT), which occurs in ~45% of all glioblastomas (Gliomas are the most common primary tumors of the brain. Glioblastoma (stage IV glioma) is the most frequent type of glioma and represents ~50% of all adult malignant primary brain tumors and ~20% of all intracranial tumors including metastases. Glioblastoma patients face dismal survival prospects; even after receiving intensive SOC therapy consisting of debulking surgery, radiotherapy, and temozolomide chemotherapy, the median overall survival is only 14.6 months . In addilastomas . On the Low grade gliomas can be subdivided into astrocytomas and oligodendrogliomas based on cellular morphology assessed by histopathological examination. These histological differences in LGGs are underlined by unique genomic and microenvironmental profiles. Genetically, astrocytomas tend to possess TP53 and ATRX mutations whereas oligodendrogliomas are characterized by mutations in the TERT promoter and co-deletion of the 1p and 19q chromosomal arms . AnalysiThe salient genomic feature that largely distinguishes LGG from glioblastoma is the mutational status of the two genes encoding the isoforms of isocitrate dehydrogenase (IDH1/2); ~80% of LGG harbor IDH mutations, compared to only ~5% of glioblastomas. Interestingly, IDH mutations are an independent prognostic factor in gliomas and are associated with increased survival in all types, including glioblastoma , 30, 39.While it is understood how IDH1 mutations directly shape the phenotypic and epigenetic landscape of glioma cells through 2-HG by significantly altering the methylome of glioma cells and directly causing the glioma CpG island methylator phenotype (G-CIMP), a strong positive prognostic indicator in glioma and glioblastoma , 41, it In addition to the putative effects of 2-HG on TME composition, there are several defining TME features that distinguish LGG from glioblastoma that may be influenced by IDH status. In both patients and animal models, the TME of LGG has a reduced immune infiltrate, produces less inflammatory cytokines, and is impaired in its ability to recruit peripheral immune cells compared to the TME of glioblastoma . In addiIn addition to immune cell composition, the structure of the brain extracellular matrix (ECM) appears to help characteristically define both LGG and glioblastoma. The structure and composition of the brain ECM is unique compared to other organs and tissues, and is dominated by glycoproteins, proteoglycans, and glycosaminoglycans (GAGs) such as heparin sulfate proteoglycans (HSPGs) and hyaluronic acid (HA). In brain tumors, the ECM is dense, leading to hypoxia and tumor aggressiveness. Given the association between ECM stiffness and tumor progression observed in epithelial tumors –51, it iGlioblastoma is characterized by a high degree of inter- and intra-tumor heterogeneity. Originally, glioblastoma was divided into 4 molecular subtypes based on bulk gene expression data: proneural (PN) characterized by aberrations in platelet-derived growth factor A (PDGFRA), TP53, and increased phosphoinositide 3-kinase (PI3K) signaling; classical (CL) characterized by epidermal growth factor receptor (EGFR) gain and phosphatase and tensin homolog (PTEN) loss underscored by chromosome 7 amplification and chromosome 10 loss, respectively; mesenchymal (MES) characterized by neurofibromin 1 (NF-1) loss and/or mutation; and neural which did not possess any characteristic genomic features  21, 22), 2221, 2In the context of many epithelial tumors, molecular and genetic variation in cancer cells has been shown to translate to phenotypic and functional variation in the TME –59. For In addition to macrophages, CD4 T cells and neutrophils are also abundant in MES gliomas  23). Wi. Wi23). However, delineation by molecular subtype does not uncover the full scope of cellular immune TME heterogeneity in glioblastoma. Unlike myeloid cells, an increased predicted presence of CD8 T cells is not associated with any molecular subtype, but rather with a hypermutated phenotype . This fiIn addition to enlisting the help of specific immune populations, tumors rely on inhibitory checkpoint molecules to shield them from immune destruction by T cells. The most studied of these molecules are programmed cell death protein 1 (PD-1) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), which canonically inhibit T cell responses in the periphery and secondary lymphoid organs, respectively . In glioDespite clear differences in TME composition between molecular subtypes, tumor-intrinsic mechanisms that influence these distinctions are poorly defined. The most obvious possibility is that cancer cell expression of subtype-defining molecular features themselves  may regAnother interesting possibility by which TME composition is regulated in a subtype-specific manner is that the increased immune infiltrate associated with MES tumors is secondary to them being more immunogenic than their non-MES counterparts . To suppThe vasculature is an important component of the TME and is often co-opted to support the growth of tumors. One histological hallmark of glioblastoma compared to low-grade glioma is high vascularity. Unlike the healthy brain, the vascular network in glioblastoma is disorganized and displays a high degree of microvascular proliferation . As suchThe brain vasculature is also endowed with unique properties owing to the existence of the BBB. The BBB functions as a highly selective barrier between the brain and the periphery, therefore its integrity and functional status significantly impact the trafficking of immune cells, proteins, antibodies, metabolites, and therapeutic agents between the circulation and the tumor. This, in turn, places BBB function as an important regulator of pathology and response to therapy. Although the BBB is often impaired in various brain malignancies , 80, 81,Gliomagenesis (cancer development) as well as gliogenesis and neurogenesis  rely on a series of shared mechanisms including notch signaling , 83, neuGlioblastomas are highly heterogeneous tumors. Although they can be classified as PN, CL, or MES based on bulk expression profiles; all glioblastomas, regardless of subtype, possess cells from the other two subtypes in varying proportions , 109. EvAcknowledging and understanding the variation of tumor-microenvironment interactions across a single tumor is of utmost clinical importance. Following primary debulking surgery, the core of the cellular tumor is removed. Thus, remaining cancer cells inhabit a unique microenvironment, rich in non-neoplastic cells, that is most likely not represented in the resected material. Along with the inflammation triggered by surgical intervention, these elements may shape the molecular profile and behavior of remaining cancer cells in as-of-yet underappreciated ways. As the aim of therapies administered in the adjuvant setting is to eradicate any non-resected tumor cells, consideration of the microenvironmental landscape of residual disease will be crucial to prevent tumor rebound and achieve long term remission.The molecular subtype of a primary tumor is not a reliable predictor of the molecular subtype of the recurrent tumor . In factInterestingly, the microenvironmental features associated with each molecular subtype in primary disease appear to be largely recapitulated in the recurrent setting, even in situations of molecular class switching . There aThe factors which regulate molecular subtype switching in recurrent glioblastoma remain unclear. While primary tumors with a lower simplicity score, indicating a higher degree of intra-tumor transcriptional heterogeneity, tend to give rise to recurrent tumors of a different molecular subtype , microenThis is in contrast to a study by Neftel et al. demonstrating that all glioblastoma meta-modules contain cells with the potential of restoring the full diversity observed in human tumors in both immunocompetent and immunodeficient hosts . HoweverMetastases arising from extracranial neoplasms are the most common manifestation of brain cancer . SimilarMetastases follow a distinct evolutionary path from their parent tumor in a site-specific manner. In line with the notion that metastases arise from clones that are best suited to colonizing specific tissues, it is believed that the unique microenvironmental architecture of each organ is the purveyor of the selective drive which guides the evolution of developing metastases. The brain microenvironment appears to exert a particularly harsh evolutionary pressure on circulating tumor cells as only a handful of epithelial malignancies are regularly capable of colonizing the brain, and even then, they do so with very poor efficiency .The absence of brain metastases derived from certain aggressive and highly metastatic neoplasms further highlights the selective nature of the brain microenvironment. Indeed, it seems that brain tropism is dictated by the specific ability of cancer cells to adapt to the brain microenvironment rather than their inherent metastatic potential. Interestingly, neoplasms originating from the same site will metastasize to the brain at different rates as a function of subtype , 129. AmBrain metastases can grow as well-demarcated entities, or as diffusely infiltrating tumors . InfiltrStudies on heterotypic cell-cell interactions between metastasizing cells and resident central nervous system (CNS) cells have largely focused on astrocytes due to their abundance in the brain, as well as their key role in the physiology of the BBB which invading cells must cross. Immediately after extravasation, invading cancer cells encounter reactive astrocytes that activate neuron-derived plasmin , 142. AcRecently, a multi-cellular communication network between astrocytes and immune cells was discovered during metastatic outgrowth in the brain . MetastaCommunication between astrocytes and cancer cells has been reported to support the development and survival of micrometastases , 147. SuThe CL molecular subtype of glioblastoma is strongly associated with an astrocytic signature , and ampOverall, the molecular and genetic profiles of cancers which commonly colonize the brain parenchyma appear to display certain features that mirror the molecular profiles of primary brain malignancies. BRAF-driven melanoma and KRAS-driven NSCLC both exhibit aberrant RAS-MAPK signaling similarly to mesenchymal (MES) glioblastoma , which iA recent study of TCGA uncovered associations between oncogenic mutations and various immune signatures irrespective of cancer ontogeny. This connection extends beyond the well-documented association of deficient mismatch repair (dMMR) and an increased cytotoxic T cell infiltrate , 155. FoThe TME is a critical regulator of disease progression and response to therapy. In fact, several novel therapeutic strategies against brain cancers leverage the microenvironment to kill tumor cells, including immune checkpoint inhibitors which have been extremely effective in other malignancies such as melanoma, lung, and bladder cancer. Checkmate 143, the first phase 3 randomized clinical trial evaluating the efficacy of adjuvant PD-1 blockade in glioblastoma using nivolumab, concluded that it did not improve overall survival compared to anti-VEGF therapy with bevacizumab . HoweverThe timing of immunotherapy is also an important consideration. As we have discussed, the microenvironmental landscape of glioblastoma evolves throughout disease progression, most notably after tumor resection and upon disease recurrence. Unsurprisingly, the timing of PD-1 blockade impacts response. In fact, recent trials have revealed that neoadjuvant PD-1 blockade with either pembrolizumab or nivolumab against treatment naïve tumors , or evenPersonalized vaccines have also shown great promise to combat brain malignancies , 168. ThA significant challenge that remains for immunotherapies in brain malignancies is the fact that even if they are successful in priming anti-tumor T cell responses, T cells still face a barrage of local immunosuppression that needs to be overcome. To relieve this inhibition, strategies are actively being developed to reverse the highly immunosuppressive milieu of the brain tumor microenvironment. For example, leveraging the high prevalence of macrophages in glioblastoma, macrophage reprogramming through blockade of CSF-1R has been highly effective in pre-clinical models .Combinatorial strategies will surely yield the most successful clinical results in the future, as they have in the context of many other malignancies. However, the success of future experimental therapies is predicated on an increased appreciation of the complex relationships that exist between the molecular identity and the microenvironmental landscape of brain tumors.LP and LW conceived the review, wrote, and edited the manuscript.The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


Cerebral autoregulation is crucial for maintaining cerebral blood flow and perfusion. In recent years, the importance of cerebral oxygenation in syncope and orthostatic intolerance (OI) has received increased attention. Cerebral tissue oxygenation can be measured by using near-infrared spectroscopy (NIRS), which determines the ratio of oxygenated hemoglobin to total hemoglobin in cerebral tissue. NIRS is non-invasive technology using near-infrared light, which displays real-time cerebral tissue oxygenation. Normal values of cerebral tissue oxygenation in healthy subjects are 60 to 80%. Head-up tilt test (HUT) offers the opportunity to observe the haemodynamic changes precipitating syncope and is, today, the standard method for the evaluation of syncope and orthostatic intolerance syndromes. In previous studies where NIRS was applied during HUT, a significant decrease in cerebral tissue oxygenation both prior to and during loss-of-consciousness in vasovagal syncope (VVS) has been observed. Interestingly, cerebral tissue oxygenation appears to decrease even before haemodynamic changes can be observed. Apart from VVS, cerebral tissue oxygenation decreases during orthostatic provocation in patients with orthostatic hypotension (OH) and postural orthostatic tachycardia syndrome (POTS), in the latter even in the absence of hypotension. Importantly, decline of cerebral tissue oxygenation in VVS and POTS during HUT may not correlate with hemodynamic changes. In this mini review, we summarize the current knowledge of the application of cerebral oximetry in syncope and orthostatic intolerance syndromes, discuss its likely value as a clinical diagnostic tool and also emphasize its potential in the understanding of the relevant pathophysiology. Syncope and orthostatic intolerance (OI) involve a variety of clinical syndromes on the basis of cardiovascular disease or autonomic dysfunction . These c2. Because oxygenated Hb and deoxygenated Hb have different absorption spectra, their proportion can be calculated  has gained increased attention since it offers the opportunity to observe absolute values of cerebral oxygenation . NIRS melculated . The prilculated .NIRS technology combined with so called diffuse correlation spectroscopy permits direct monitoring of cerebral blood flow in addition to oxygenation . In shorHead-up tilt test (HUT) is an established method for the evaluation of unexplained syncope and orthostatic intolerance by its opportunity to observe the haemodynamic changes during orthostatic provocation . By applWhen standing up, venous blood is pooled in the lower extremities and splanchnic area which leads to decreased venous return and reduced cardiac output. In turn, decreased cardiac output initiates various autonomic responses that if insufficient or impaired, ultimately may result in decreased cerebral perfusion and syncope . The impAnother study using diffuse correlation spectroscopy flow-oximetry found that a threshold of ~50% cerebral blood flow decrease during HUT can be applied in order to separate pre-syncopal patients from controls. Potentially, continuous monitoring of cerebral tissue oxygenation and blood flow may provide predictive information for impending VVS during HUT, possibly both shortening the test and avoiding the need for induction of syncope , 21.Cerebral oximetry may also offer the possibility to analyse the syncope mechanism in potentially overlapping diagnoses such as VVS, postural orthostatic tachycardia syndrome (POTS), or OH by providing characteristic signal patterns during HUT , 11 Fig. DiffereAn issue with HUT is the apparent high false-positive and false-negative rates in adults  althoughKim et al.  using ceCerebral tissue oxygenation declines during orthostasis in patients with POTS , 15 Fig. POTS isNIRS and diffuse correlation spectroscopy flow-oximetry have definite potential for practical measurements of cerebral perfusion. They are both safe, non-invasive, applicable at the bedside, and suitable for quantitative measurements and continuous monitoring with little operator-dependency. Wireless NIRS devices have recently been validated in animals  and are The limitations of cerebral oximetry are mainly technical. NIRS does not measure cerebral blood flow directly, unless some form of flow tracer is used, e.g., a short breath of 100% oxygen or an injection of a contrast agent . As prevFurther, NIRS displays a great variety in the human anatomy of vessels and non-vascular tissue, where baseline values vary by ~10% between individuals. Thus, cerebral oximetry is more suitable for detecting intra-individual rather than inter-individual changes . Also, tFinally, cerebral oximetry with NIRS measures oxygen saturation levels in the regions where the probes are located and does not provide information on cerebral saturation in remote parts of the brain. A significant redistribution of the cerebral blood flow values during HUT has previously been found , with a As described in this review, cerebral oximetry has been increasingly used in various experimental settings in the recent years. However, cerebral oximetry is yet to find its role as an established method in the clinical settings of syncope and orthostatic intolerance. The future applications of cerebral oximetry can be broadly divided into two partly overlapping major goals: First, cerebral oximetry may aid in the understanding of pathophysiological mechanisms underlying syncope and orthostatic intolerance, the relationship between haemodynamic changes and cerebral autoregulation, and also serving as a complement to the current methods of cerebral circulation assessment. The cerebral oximetry may be applied for better monitoring of coupling between haemodynamic changes and characteristic symptoms observed in both VVS , 11, 20 As an example, monitoring of cerebral tissue oxygenation may provide predictive information for impending VVS during HUT, avoiding the need for induction of syncope , 21. TheCerebral oximetry with near infrared spectroscopy is a harmless, non-invasive technique which provides the opportunity to measure real-time regional cerebral tissue oxygenation. With the addition of diffuse correlation spectroscopy, simultaneous estimation of cerebral blood flow can be made. These techniques are able to demonstrate different patterns of cerebral deoxygenation during orthostatic provocation in patients with various types of syncope and orthostatic intolerance, before any haemodynamic changes can be observed. Furthermore, the addition of cerebral oximetry to the established head up tilt test allows a more sensitive detection of orthostatic intolerance and may reflect disrupted homeostasis of cerebral oxygenation in POTS. With increasing use in research, cerebral oximetry may be able to provide information about factors related to cerebral hypoperfusion as well as clues to hitherto unknown factors behind syndromes associated with recurrent syncope and orthostatic intolerance.Concept and design, drafting the article, critical revision of the article, and approval of the article: IK, HH, EB, FR, RS, AF, and VH. Funding secured by: AF and VH. Other: IK and AF.AF reports personal fees from Medtronic Inc. and Cardiome Corp., and patent royalties from Thermo Fisher Scientific outside the submitted work. RS reports consultancy for Medtronic Inc., Member of Speakers' Bureau Abbott Labs and Stockholder in Edwards LifeSciences, Boston Scientific Inc. and AstraZeneca PLC. VH reports previous educational congress grant from Boston Scientific Inc. outside the submitted work and Stockholder in Swedish Orphan Biovitrum AB (publ). EB has been employed by AstraZeneca after completion of this study. The remaining authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.


In oncology, next generation sequencing and comprehensive genomic profiling have enabled the detailed classification of tumors using molecular biology. However, it is unrealistic to conduct phase I–III trials according to each sub-population based on patient molecular subtypes. Common protocols that assess the combination of several molecular markers and their targeted therapies by means of multiple sub-studies are required. These protocols are called “master protocols,” and are drawing attention as a next-generation clinical trial design. Recently, several reviews of clinical trials based on the master protocol design have been published, but their definitions of these such trials, including basket, umbrella, and platform trials, were not consistent. Concurrently, the acceleration of the development of new statistical designs for master protocol trials has been underway. This article provides an overview of recent reviews for master protocols, including their statistical design methodologies in Oncology. We also introduce several examples of previous and on-going master protocol trials along with their classifications by some recent studies. With this development, targeted therapies are being established for some tumor types based on genetic mutations . If patiThree challenges that have been particularly difficult in common clinical trials are possibly alleviated by conducting multiple clinical trials based on a master protocol . First, This article begins with an overview of the history from biomarker-based trial design to master protocol trial, and subsequently summarizes clinical trials using master protocols in oncology based on recent general theories of master protocol design . We intr2EGFR gene mutation-positive inoperable, recurrent, or metastatic non-small cell lung cancer  from the


Mitochondrial dysfunction has been linked to many diseases including organ degeneration and cancer. Mesenchymal stem cells/stromal cells (MSCs) provide a valuable source for stem cell-based therapy and represent an emerging therapeutic approach for tissue regeneration. Increasing evidence suggests that MSCs can directly donate mitochondria to recover from cell injury and rescue mitochondrial damage-provoked tissue degeneration. Meanwhile, cancer cells and cancer stromal cells also cross-talk through mitochondrial exchange to regulate cancer metastasis. This review summarizes the research on MSCs and their mitochondrial transfer. It provides an overview of the biology, function, niches and signaling that play a role in tissue repair. It also highlights the pathologies of cancer growth and metastasis linked to mitochondrial exchange between cancer cells and surrounding stromal cells. It becomes evident that the function of MSC mitochondrial transfer is a double-edged sword. MSC mitochondrial transfer may be a pharmaceutical target for tissue repair and cancer therapy. Mitochondria are well known as biological engines that generate energy. They decompose carbohydrates to produce adenosine triphosphate (ATP) through oxidative phosphorylation (OXPHOS), providing most of the energy needed for metabolism and movement in living organisms ,2. At thMitochondrial dysfunction is one of the hallmarks of aging and is associated with a large proportion of human diseases ,3. ROS iMesenchymal stem cells/stromal cells (MSCs) are generally derived from bone marrow  and adip+ for high glycolytic flux [However, mitochondrial transfer also plays a positive role in tumor growth. Transferred mitochondria produce detrimental effects to health as they sustain the growth of cancer cells by maintaining macromolecular biosynthesis and cytoplasmic pools of NADtic flux . Worse stic flux . Similartic flux .In brief, mitochondrial transfer is a double-edged sword. In this mini-review, we aim to illustrate the beneficial and harmful effects of MSC mitochondrial transfer, as well as to discuss opportunities for future stem cell research.Numerous studies have demonstrated that transfer of mitochondria between MSCs and damaged tissue is a key mechanism for tissue repair. The first description of the transfer was the acquisition of functional mitochondria in A549 ρ° cells with mtDNA deletions or defects when they were co-cultured with human MSCs . The recStudies have shown that it is possible to transfer human bone marrow-derived MSC (BM-MSC) mitochondria to animal embryonic and adult cardiomyocytes . Co-cultIntriguingly, mitochondria are not confined to a unidirectional transfer from MSCs to injured cells. In co-culture of human BM-MSCs and coronary artery vascular smooth muscle cells (VSMCs), mitochondrial transfer has been demonstrated to be bidirectional with no preferential direction of movement . TransfeEscherichia coli lipopolysaccharide, mouse BM-MSCs reduced leukocyte numbers, restored surfactant secretion and enhanced survival of mouse lungs [in vivo and in vitro has been shown to promote their phagocytic capacity and suppress pro-inflammatory cytokine secretions in an acute respiratory distress syndrome environment [E. coli pneumonia [In a study of acute lung injury induced by se lungs . Mitochose lungs . Mitochose lungs , especiase lungs . Apart fironment ,29. The neumonia  may warrAstrocytes and neuron-like pheochromocytoma cells have been shown to receive mitochondria from MSCs in co-cultivation, as revealed by fluorescence microscopy . MitochoInflammation is an essential part of the malignant microenvironment and contributes to tumor progression . In tumoAlthough mitochondrial transfer from MSCs to damaged cells has produced encouraging results in tissue repair, the effects on cancer cells are not desirable . Tumor gAcquisition of mitochondria also results in greater chemoresistance of breast cancer cells to doxorubicin . SurprisIn addition to solid cancers, mitochondrial transfer may also worsen the outcome of hematological cancers. When acute myelogenous leukemia (AML) cells received mitochondria from BM-MSCs, they demonstrated increased OXPHOS and ATP production, as well as chemoresistance to cytarabine . MoreoveAt present, the theory accepted by most scholars is the formation of TNTs between the recipient cells and the donor cells with complete transfer of mitochondria achieved through active transport ,25–28,31in vivo and deliver mitochondria in microvesicles to the epithelia from bone marrow-derived stromal cells [Gap junctions are also shown to mediate mitochondria transfer of MSCs. Connexin 43-containing gap junction channels has been particularly well observed in a mouse model of acute lung injury al cells . Blockinal cells .mtDNA from MSCs is transferred via extracellular vesicles. It has been recently demonstrated that migration of mtDNA can take place via exosomes . ExtraceIt has also been reported that mitochondria transfer can be achieved by selective loss of donor nuclei after complete cell fusion .The main mechanisms of intercellular mitochondrial transfer adopted so far are shown in Generally, mitochondrial transfer is directional, which is determined by some factors. (i) Several studies have demonstrated that directionality of mitochondrial transfer is associated with cytoskeletal microfilaments in microvesicles of connected tubular structures ,55,56. PMitochondrial biogenesis and respiration are critical for tumor cell growth, survival and metastasis . Dong etMyocardial ischemia and reperfusion results in severe mitochondrial loss that can lead to ischemic necrosis of cardiomyocytes . ClinicaMitochondrial transfer is a ubiquitous phenomenon that is associated with various physiological and pathological activities of the body. Therefore, mitochondrial treatment through mitochondrial transfer has potentially broad applications. We can effectively treat with MSCs by mitochondrial transfer to restore normal physiological functions of cells and recover patients from diseased condition. Meanwhile, inhibition of mitochondrial transfer from stromal cells to cancer cells may serve a potential therapeutic target.


Raf Kinase Inhibitory Protein (RKIP) is a highly conserved kinase inhibitor that functions as a metastasis suppressor in a variety of cancers. Since RKIP can reprogram tumor cells to a non-metastatic state by rewiring kinase networks, elucidating the mechanism by which RKIP acts not only reveals molecular mechanisms that regulate metastasis, but also represents an opportunity to target these signaling networks therapeutically. Although RKIP is often lost during metastatic progression, the mechanism by which this occurs in tumor cells is complex and not well understood. In this review, we summarize our current understanding of RKIP regulation in tumors and consider experimental and computational strategies for recovering or mimicking its function by targeting mediators of metastasis. Metastasis suppressors are a group of physiological proteins that function to block metastatic progression of tumors. Unlike tumor suppressors, metastasis suppressors do not affect initiation and growth properties of the primary tumors, but rather inhibit the dissemination mechanisms of tumor cells, such as invasion through tissue, intravasation/extravasation, and metastatic colonization. Similar to tumor suppressors, inactivation of metastasis suppressors is a common step in a cancer’s progression into a metastatic disease. This transition can take place by genetic loss of function through deletions or mutations, by epigenetic silencing of the suppressors through DNA methylation and histone modifications, by downregulation of transcriptional machinery controlling the suppressor expression, or by increased rates of post-transcriptional degradation through proteasome and miRNAs. Understanding the details of the regulation and function of metastasis suppressors can create therapeutic opportunities to either restore or mimic the role of these proteins in metastatic cancers. Furthermore, metastasis suppressors and their functional gene networks can be used as prognostic and predictive markers in the clinic for metastatic progression and survival.Raf kinase inhibitory protein (RKIP), also known as phosphatidylethanolamine binding protein 1 (PEBP1), is a highly conserved protein that is commonly lost or downregulated in cancers. Low RKIP expression correlates very strongly with metastatic phenotype in the majority of cancers, including prostate, breast, pancreatic, lung, cervical cancers and gliomas ,3. Due tAt the molecular level, RKIP functions as an inhibitor of kinase activity. It was originally identified as a direct binding partner for Raf kinase , and mulRKIP downregulation or total loss is a common event in metastatic solid tumors. However, the mechanism by which tumor cells lose or deactivate RKIP as they become more invasive and metastatic remains elusive. Evidence based on TCGA databases for a variety of cancers suggests that it is usually not a genetic or mutational event A and onlRKIP’s ability to shift tumor cells into a non-metastatic phenotype by reprogramming kinase networks presents a unique opportunity not only to understand molecular mechanisms of metastatic progression, but also to counteract these mechanisms as a therapeutic strategy. In this review, we will cover what is known about mechanisms of RKIP loss in metastatic solid tumors and discuss strategies for recovering its function, with a particular focus on mimicking its downstream effects on metastatic signaling and gene expression.Promoter methylation: Promoter methylation is a well-characterized mechanism for epigenetic silencing by which gene transcription is halted through transcription factor inaccessibility, without any genetic alterations. Several studies of tumors, including gastric adenocarcinomas ,19, esopHistone modifications: In the prostate cancer cell line DU145, the histone deacetylase (HDAC) inhibitor trichostatin A (TSA) caused a potent increase in RKIP levels , raisingThese clinical and experimental findings suggest the use of demethylating agents as a potential strategy for inducing RKIP expression in metastasis cancers. Labbozzetta’s study showed decreased RKIP promoter methylation and increased RKIP mRNA and protein levels in SUM159 cells treated with various doses of the demethylating agent 5-Azacytidine (5-AzaC) . Guo et PSD-95), discs-large tumor suppressor (Dlg), and tight junction protein-1 (ZO-1) containing scaffold protein that promotes melanoma progression and metastasis, can silence RKIP transcription by activating SNAIL expression through ERK1 and ERK2  and NFκB signaling [The role of transcriptional silencing of RKIP in metastatic progression is not well understood. The best characterized transcriptional regulator of RKIP is the epithelial-to-mesenchymal transition (EMT) protein SNAIL. Beach et al. originally identified SNAIL as a direct transcriptional repressor of RKIP in prostate cancer cell lines PC3 and DU145  and demoignaling .SNAI1), BACH1 expression is significantly inversely correlated with RKIP expression in the TCGA breast cancer patient database, suggesting that BACH1 may be the main negative regulator of RKIP in breast cancer , Platelet-derived Growth Factor Receptor (PDGFR), and Raf) in non-small cell lung cancer (NSCLC)  and in pClinical implications of RKIP expression in liquid cancers, reviewed in detail by Lamiman et al. , is a fiDespite its inhibitory effect on extravasation and tissue infiltration in myeloid sarcoma, loss of RKIP seems to be a marker for good prognosis in AML , contrarIn non-Hodgkin’s lymphoma B cells, Rituximab, an FDA-approved chimeric anti-human CD20 monoclonal antibody, sensitizes resistant tumor cells to drug treatment by inducing RKIP expression leading to down-regulation of ERK phosphorylation and the anti-apoptotic gene Bcl-XL (B-cell lymphoma–extra large) . This isTaken together, these studies demonstrate that it is important to take into account specific cell types when assessing the association of RKIP with clinical outcome. Particularly when comparing liquid versus solid tumors, the impact of the different microenvironments as well as the unique intracellular regulators on tumor cell gene expression and signaling could lead to different mechanisms for regulating RKIP at multiple levels, including epigenetic/transcriptional, translational, and post-translational.Inhibiting mechanisms that suppress RKIP transcription is a viable strategy to reactivate RKIP function in metastatic cancers. As discussed above, this method could revert the invasive phenotype in certain cancers. However, the presence of post-transcriptional and post-translational mechanisms to downregulate RKIP as well as the possibility of off-target effects may limit the success of these approaches. An alternative approach is to elucidate downstream kinase and gene networks regulated by RKIP and mimic its molecular and cellular function therapeutically. Since RKIP is an inhibitor of kinases across metastatic cancers, identifying its kinase targets can reveal key signaling mechanisms of invasion and metastasis that are targetable with small molecule inhibitors. Kinomic and transcriptomic reprogramming by RKIP in cancers can be used as a guide to develop anti-metastatic therapies and build gene signatures for precision medicine.RKIP regulates the activity of multiple kinase pathways that are important for metastasis. As an inhibitor of the Raf-Mek-Erk cascade, RKIP binds to Raf-1 and blocks activation of downstream mitogen-activated protein kinases (MAPKs) ,62,63. RPharmacological inhibition of these pathways can potentially mimic RKIP. Raf and Mek inhibitors have been extensively studied for their anti-tumorigenic and anti-metastatic activities and are in clinical trials for metastatic cancers . InhibitRKIP’s anti-metastatic function is at least partially mediated through its effect on the tumor microenvironment. Rosner and colleagues demonstrated that RKIP over-expression in metastatic TNBC mouse models robustly blocks recruitment of tumor-associated macrophages (TAMs) into the tumors through a mechanism dependent upon the chemokine CCL5 (C-C motif chemokine ligand 5) . TAMs arMore broadly, using species-specific RNA sequencing in a xenograft TNBC mouse model, Bainer et al. demonstrated that gene expression in metastatic breast tumors is widely correlated with gene expression in local stroma of both mouse xenografts and human patients . MoreoveComputational strategies are extremely useful in identifying critical signaling pathways and targetable factors, especially when powered by patient-derived data. Using known biological interactions  as filters is a powerful method while building networks because it reduces noise . RKIP, aTo systemically identify downstream mediators of RKIP, Rosner and colleagues have employed integrated approaches that combine statistical/computational analysis of breast cancer gene expression data and experimentally-validated gene interactions. Dangi-Garimella et al. first experimentally identified a pro-metastatic signaling cascade involving Myc/LIN28/let-7 as an RKIP target . Then, YExploring and expanding RKIP-regulated gene networks using patient-derived expression data also allow for developing predictive and prognostic gene signatures that have mechanistic relevance to specific patient cohorts. After identifying RKIP-regulated signaling networks in tumors and their microenvironment, the Rosner group generated several RKIP pathway-based gene signatures for predicting metastasis-free survival of breast cancer patients ,7,8,9,10With the completion of TCGA and ease of access to clinical sequencing data from multiple studies, building clinically relevant hypothetical gene networks and signatures is becoming less challenging. Gene signatures built on experimentally validated mechanistic gene-gene interactions can (1) help identify/stratify patients for guided/personalized treatment, (2) be used as biomarkers for predicting drug efficacy or sensitivity in patients, and (3) be combined with machine learning methods for drug discovery or drug repurposing for a particular biological function. Conceptually, novel anti-metastatic therapies can be discovered as long as the therapeutic approach being tested is able to target genes in patients identified as high risk by RKIP-related gene signatures. In parallel, therapeutic treatments that mimic RKIP’s anti-metastatic functions would be more effective in patients who are at high risk for metastasis based on their RKIP pathway signature score.In sum, RKIP is an important suppressor of metastasis that would be most effective if induced in metastatic cells. However, even in the absence of RKIP protein, it is possible to leverage RKIP targets and patient data to identify novel targets such as specific kinases that, if inhibited together, can mimic the anti-metastatic properties of RKIP and make tumors more homogeneous and more susceptible to conventional cytotoxic therapy.


Even though data suggest that palliative care (PC) improves patient quality of life, caregiver burden, cost, and intensive care unit (ICU) length of stay, integration of PC in the ICU is far from being universally accepted. Poor understanding of what PC provides is one of the barriers to the widespread implementation of their services in ICU. Evidence suggests that the availability of specialist PC is lacking in most European countries and provided differently depending on geographical location. The aim of this systematic review is to compare the numbers and types of PC interventions and gauge their impact on stakeholder outcomes and ICU resource utilisation.We will undertake a systematic review of the published peer-reviewed journal articles; our search will be carried out MEDLINE, Embase, Cochrane, CINAHL, and PsycINFO. The search strategy will include variations in the term ‘palliative care’ and ‘intensive care’. All studies with patient populations undergoing palliative care interventions will be selected. Only full-text articles will be considered, and conference abstracts excluded. There will be no date restrictions on the year of publications or on language. The primary aim of the present study is to compare the numbers and types of PC interventions in ICU and their impact on stakeholder  outcomes. Reporting of findings will follow the Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines.This review will provide insight into the implementation of palliative care in ICU, elucidate differences between countries and health systems, reveal most effective models, and contribute to identifying research priorities to improve outcomes.CRD42018094315)International Prospective Register of Systematic reviews PROSPERO ( Palliative care (PC) is a holistic approach which incorporates management of physical, psychological and spiritual symptoms, communication regarding goals of care, support for clinicians and families, and planning for care transitions in patients with critical illness . Even thRecently, existing evidence was organised to address: (1) opportunities to alleviate physical and emotional symptoms, improve communication, and provide support for patients and families; (2) models and specific interventions for improving ICU palliative care; (3) available resources for ICU palliative care improvement; and 4) ongoing challenges and targets for future research . However ongoing The aim of this systematic review was to compare the numbers and types of PC interventions and gauge their impact on stakeholder outcomes and ICU resource utilisation.The primary aim of this study is to compare the numbers and types of PC interventions in ICU, and their impact on patient and family outcomes.Assess the models for integrating palliative care into the ICUCompare evidence from different regions of the world .Secondary aims are toThis will enable us to identify research priorities and formulate a research agenda to improve palliative care in ICU.In order to assess the current state of evidence, we propose to describe the numbers and types of PC interventions and gauge their impact on stakeholder  outcomes and ICU resource utilisation. We also intend to assess the different types of PC and their variable integration in European versus non-European countries and provide data to develop future interventions to improve PC in the ICU.https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=94315) (CRD42018094315) and will be reported using Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines in the peer-reviewed literature [This systematic review protocol is registered with the PROSPERO International Prospective Register of Systematic Reviews  admitted to the intensive care unit or high-dependency areas.Adult patients (Terms used:(burn unit*[tiab] OR coronary care unit*[tiab] OR respiratory care unit*[tiab] OR intensive cardiac care [tiab] OR “Intensive Care Units”[Mesh:NoExp] OR icu [tiab] OR high dependency unit [tiab] OR hdu [tiab]) OR “Burn Units”[Mesh] OR “Coronary Care Units”[Mesh] OR “Respiratory Care Units”[Mesh].Palliative care interventions occurring in ICU.Terms used:Patients that did not receive any PC interventions.Terms used: none.The number and type of PC interventions as identified by a working group funded by the Robert Wood Johnson Foundation  in ICU in Europe, North America, South America, and Asia . We willTerms used: none.Controlled trials (randomised and non-randomised). Case reports, case series, editorials/commentaries, opinion papers, studies with no outcome data, small studies (< 30 patients), publications only as abstracts, and (non-systematic) review papers will not be included.Terms used: AND (mask*[tw] OR blind*[tw])) OR “latin square”[tw] OR placebos [mh] OR placebo*[tw] OR random*[tw] OR research design [mh:noexp] OR comparative study [pt] OR evaluation studies [pt] OR follow-up studies [mh] OR prospective studies [mh] OR cross-over studies [mh] OR control [tw] OR controll*[tw] OR prospectiv*[tw] OR volunteer*[tw]) NOT )ORSystematic [sb].The search terms above are specific to PubMed/MEDLINE and will not generalise to other search engines. Search strategies for the other databases were derived from the terms used in PubMed.With the assistance of a librarian, we designed a Boolean search strategy which includes variations in the term ‘palliative care’ and ‘intensive care’. We carried out the search strategy on the following databases: MEDLINE, EMBASE, Cochrane, CINAHL, and PsycINFO. The search terms that were used are outlined above. There were no date restrictions on the year of publications or on language. The preliminary peer review/scoping of the literature was conducted between 02 February 2018 and 19 May 2018. The formal systematic search of the literature was completed on 19 May 2018. The systematic search was conducted by a professional librarian (IvD) and assisted by three of the content experts .All adult patients (> 18 years of age) admitted to the intensive care unitPalliative care interventionInclusion criteria:(Paediatric)  populationsCase seriesOpinion paper/commentaryReview article (non-systematic review)Lack of quantitative data< 30 patients in study populationConference abstracts/grey literatureExclusion criteria include the following:After retrieving initial results, results were amalgamated and duplicates removed using RefWorks. The remaining studies were loaded onto the online systematic review software Covidence™. There was a total of five independent reviewers  who independently performed the title and abstract screening. Each title/abstract was reviewed independently by two reviewers. Where there was disagreement between reviewers, conflict was resolved between the two reviewers, erring on the side of inclusivity. A fifth author was consulted where consensus is not reached. Full texts will be retrieved for inclusion based upon the defined criteria. We will screen the references of included studies for potential publications not identified by the search strategy.Our main objectives are to establish the number, type, and effectiveness of PC interventions in ICU, and to ascertain differences between Europe, North America, South America, and Asia. We will attempt to categorise outcomes of PC interventions according to previously established domains , to circumvent variations in terminology. We will also endeavour to assess the models for integrating palliative care into the ICU, identify research priorities, and formulate a research agenda to improve palliative care in ICUs.Data will be extracted onto a customised data extraction sheet by two independent reviewers. Conflicts will be resolved by discussion between the reviewing authors. A third author will be consulted where consensus is not reached.Study data: year of data collection, year of publication, type of study, country of study, first author name, journal, total number of patients, clinical setting, and primary and secondary outcomesPatient population data: age, primary diagnosis, sex, life-limiting conditionPalliative care intervention data: palliative care consults, end-of-life care, terminal care, advance care planning, living wills, ethics consultation, family meetings, and symptom managementOutcome data: data including but not limited to: patient/family-, clinician-, system-, and content-related factors. These include patient- and family-centred care, communication, continuity of care, emotional and practical support of patients and families, symptom management and comfort care, spiritual support, and emotional and organisational support for ICU clinicians.Variables to be extracted will include but not be limited toWhere the study data is missing, we will attempt to contact the corresponding author.Methodological quality of included randomised control trials will be assessed using Cochrane Collaboration’s tool for assessing risk of bias . The folMethodological quality of included non-randomised trials will be assessed using the ROBINS-I tool. Seven domains of bias will be assessed including confounding, selection bias, bias in measurement classification of interventions, bias due to deviations from intended interventions, bias due to missing data, bias in measurement outcomes, and bias in selection of the reported result . The risTo assess the risk of bias, we will rely on the information presented in the published literature. No reviewer will assess risk of bias for manuscripts they have participated in as an author.The initial analysis will be of a descriptive nature. The palliative care interventions and outcomes will be described. Subgroup analyses will include PC intervention incidence by region . Where there is homogeneity between studies in the palliative care interventions used and measured outcomes, we will compare outcomes.I2 methodology. I2 values > 50% and > 75% are considered to indicate moderate and significant heterogeneity among studies, respectively. All p values will be two-tailed and considered statistically significant if < 0.05.We will use the Mantel-Haenszel models for all dichotomous outcomes and we used the inverse variance method for the continuous outcomes. For continuous measures, we will calculate the mean differences. A random effects model will be used to analyse the data. Results will be presented as odds ratios with 95% confidence intervals for dichotomous outcomes. The meta-analysis will be carried out using review manager (‘Revman’) for Mac . Statistical heterogeneity will be assessed using the The strength of the body of evidence will be addressed using the GRADE  system . Any ameWe will conduct a modified Delphi process to develop further recommendations for clinical practice and future clinical trials. The first step will consist of the working group developing draft recommendations; then, for the subsequent Delphi steps, we anticipate expanding to 20–25 members of the European Society of Intensive Care (ESICM) Ethics Committee with broad geographic (country) representation.Patients admitted in ICU are often at high risk of dying and require invasive interventions or intensive monitoring. Among survivors, long-lasting sequelae affect patients’ quality of life, resulting in physical, cognitive and psychosocial complications . PalliatIntegration of palliative care in ICU has been the topic of extensive research in the recent years. Previous systematic reviews have highlighted the heterogeneity of the PC interventions and the lack of consistent meaningful, multifaceted outcomes. We aim to bring together the evidence behind diverse interventions and outcomes of palliative care interventions in intensive care. This will facilitate the identification of key interventions which are consistently associated with positive clinical outcomes. Equally, we may be able to identify the lack of evidence behind specific interventions and outcomes that are potentially useful. This process will enable clinicians and researchers to identify the best interventions and outcomes for future clinical trials.


Neuropathic pain in cancer is common and debilitating. It is important to differentiate neuropathic pain from other cancer-related pains as it is associated with worse pain outcomes and requires different treatment strategies. This review summarises recent updates to pain classification, aetiology, pain assessment and current recommendations for treatment in patients with cancer-related neuropathic pain. Neuropathic pain is defined as “pain caused by a lesion or disease affecting the somatosensory system”  and may Neuropathic pain is different from nociceptive pain, which is defined as “pain that arises from actual or threatened damage to non-neural tissue and is due to the activation of nociceptors” . In nociNeuropathic cancer pain is associated with poor outcomes ,8. A stuIn recognition of the importance of identifying neuropathic pain, the latest International Association for the Study of Pain (IASP) classification of chronic pain for International Classification of Diseases (ICD-11) identifies specific codes for chronic neuropathic cancer pain (neuropathic pain caused by tumour), as well as neuropathic pain caused by treatments, such as chemotherapy or radiotherapy . The IASThe aetiology of cancer-related neuropathic pain is diverse. Cancer-related neuropathic pain is conventionally subdivided into tumour-related and treatment-related pains. Not all pain in a cancer patient is cancer-related; pain from comorbid diseases is common, particularly in older patients . About tNCP may result from direct infiltration by the primary tumour or metastases into components of the peripheral or central nervous system. Examples of involvement of the peripheral nervous system include invasion of the brachial plexus by thoracic tumours, or invasion of the lumbosacral plexus by abdominal or pelvic tumours. A typical example of involvement of the central nervous system is spinal cord compression resulting from vertebral collapse due to bony metastatic disease.Paraneoplastic neurological syndromes can also occur, resulting from remote effects of cancer mediated by the immune system . They caCancer therapy-induced neuropathic pain can result as an unintended consequence (side effect) or complication from cancer treatments, including surgery, radiotherapy and chemotherapy. Surgical intervention may cause direct damage to peripheral nerves. Examples of interventions commonly associated with post-traumatic neuropathic pain syndromes include mastectomy and thoracotomy ,10.Radiation treatment can result chronic painful radiation-induced neuropathy. Delayed local damage to the nervous system in the field of radiotherapy is common , sometimChemotherapy-induced peripheral neuropathy (CIPN) is a common, painful and dose-limiting side effect of chemotherapy . It is gClinically, neuropathic pain is a heterogeneous entity, comprising many and varied positive and negative symptoms. Positive symptoms include pain, both spontaneous and evoked. Spontaneous pain can be continuous or paroxysmal. Evoked pain can result from non-nociceptive stimuli (e.g. pressure from tight clothes or stroking) causing allodynia, or as an increased response to a nociceptive stimulus causing hyperalgesia ,18. CharNeuropathic pain can be difficult to identify, particularly in the context of cancer pain, where other processes, such as pre-existing neurological disease or muscle spasticity from disorders of the motor system, may confuse the clinical picture . This haIn an effort to address this, in 2016 the International Study for the Study of Pain (IASP) Special Interest Group on Neuropathic Pain (NeuPSIG) proposed an updated grading system for assessment of neuropathic pain, for use in both clinical and research settings . This syDiagnosis of neuropathic pain in cancer is no different from other clinical diagnoses, relying upon comprehensive clinical history, examination and diagnostic tests. The NeuPSIG grading system and other screening tools can be usefully applied in clinical practice to identify probable cases of neuropathic pain, with little deviation from normal practice. For example, the NeuPSIG grading system starts with clinical history. This should include sensory descriptors suggestive of a neuropathic mechanism  with a relevant neurological lesion, and distribution of these symptoms in the corresponding neuroanatomical distribution. Clinical examination for sensory changes may be a little more involved than in routine clinical practice, but is still feasible at the bedside. It involves assessment of touch, vibration, pinprick, cold and warmth using routinely available tools, such as a cotton bud, tuning fork, toothpick and teaspoons in warm and cool water. The grading system indicates that only one sensory abnormality needs to be present to satisfy this criterion. Lastly, many of the diagnostic tests that would support a definite diagnosis of neuropathic pain according the NeuPSIG are routinely performed anyway, such as computed tomography or magnetic resonance imaging. Other more specialist tests may include neurophysiological tests, such as nerve conduction velocity for example .The NeuPSIG criteria have not yet been universally adopted as the reliability (inter-rater and test-retest) and applicability in clinical practice and research has not been established . Other sAnother approach to pain assessment generally reserved for use in research settings is quantitative sensory testing (QST). QST is a detailed assessment of sensory function and provides information about the underlying neurobiological mechanisms of pain processing. A standardised QST protocol published by the German Neuropathic Pain Consortium (DFNS) in 2006  has beenThe evidence base for management of cancer-related neuropathic pain is limited. There is no clear consensus for first-line or step-wise treatment of cancer-related neuropathic pain ,35, whicGabapentin, pregabalin, duloxetine and TCAs (doses of ≤75 mg/day) are recommended in the ESMO guidance as single agents for first-line treatment of neuropathic pain in cancer. This recommendation has been extrapolated from systematic reviews in non-cancer related neuropathic pain. For example, a 2015 systematic review and meta-analysis of pharmacotherapy for neuropathic pain in adults found that the numbers needed to treat were 3.6 for TCAs, 6.4 for serotonin-noradrenaline reuptake inhibitors (mainly duloxetine), 7.7 for pregabalin and 7.2 for gabapentin . They alSome studies have examined the role of adjuvants specifically in neuropathic pain in cancer but the data are less conclusive. A systematic review in 2017 examined the role of adjuvants in treating cancer pain, both purely neuropathic and mixed cancer pain . They inCancer-related neuropathic pain can also be treated using opioids or non-opioids, in combination with TCAs or anticonvulsants where required. The evidence for this is not conclusive, however. A systematic review in 2011 examined the effect of adding antidepressant or antiepileptic drugs to opioids for cancer pain that was largely caused by neuropathic mechanisms. Clinical and methodological heterogeneity precluded meta-analysis but a narrative analysis found that the addition of these adjuvants to existing opioid analgesia provided a modest improvement in pain intensity after 4 to 8 days, but unlikely more than 1 point on a 0–10 numerical rating scale, and with increased risk of adverse events . The eviOther treatment options discussed in the ESMO guidance include ketamine and interventional treatments. Ketamine is an N-methyl-D-aspartate (NMDA) antagonist which has been used to treat refractory cancer pain, including neuropathic pain, but current evidence is insufficient to determine the benefits and harms associated with this treatment . InterveAnother evolving approach to analgesia, including in cancer-related neuropathic pain, is the concept of mechanism-based pain management ,42. ThisNon-pharmacological interventions are also important in multimodal management of neuropathic cancer pain, as in all forms of cancer pain. It is well-recognised that inadequate patient education can provide a barrier to effective pain management in cancer ,44. TherConsiderable future research challenges for neuropathic pain in cancer lie ahead. Priority areas for research include cancer pain assessment, pain neurobiology and targeted therapies. Comprehensive and accurate cancer pain assessment is essential, not only to differentiate neuropathic from nociceptive pain, but also in more precisely profiling the characteristics of neuropathic pain. It is increasingly recognised that neuropathic pain actually comprises a range of different subgroups or so-called sensory profiles ,50. Thes