Multiple mathematical models of diffusion-weighted magnetic resonance imaging combined with prognostic factors for assessing the response to neoadjuvant chemotherapy and radiation therapy in locally advanced rectal cancer.
PURPOSE
To investigate whether the apparent diffusion coefficient (ADC), intravoxel incoherent motion (IVIM), and stretched exponential model (SEM) based on histogram analyses derived from the whole-tumor volume combined with prognostic factors can be used to assess the response to chemotherapy and radiation therapy (CRT) in locally advanced rectal cancer (LARC).


MATERIALS AND METHODS
This study included 60 patients with LARC who underwent diffusion-weighted imaging with 9b values (0-1000s/mm2) before CRT. Histograms derived from the whole-tumor volume were used to obtain the ADC, IVIM (Dslow, Dfast, and f), and SEM parameters (distributed diffusion coefficient (DDC) and α). The histogram metrics and prognostic factors before CRT were compared between pathological complete response (pCR) and non-pCR patients. The receiver operating characteristic (ROC) and the area under the ROC curve (AUC) were generated to analyze the histogram metrics and prognostic factors.


RESULTS
A significant difference was only found in the tumor volume between the pCR and non-pCR groups (p = 0.033, AUC = 0.740). The ADC mean, DDC median, and most of the histogram metrics were significantly lower in the pCR group than the non-pCR group (p = 0.000-0.025), and AUC was highest for the ADC mean (0.890). Only the Dslow median differed significantly between the two groups (p = 0.023, AUC = 0.721). However, the Dfast, f, and α histogram metrics did not differ significantly between the pCR and non-pCR groups. The AUC for the ADC mean combined with the tumor volume was 0.908, with a sensitivity of 100% and specificity of 81%. The inter-observer agreements were good or excellent for the ADC and SEM histogram parameters but generally fair for IVIM.


CONCLUSION
The whole-tumor ADC mean combined with the tumor volume was highly accurate for predicting pCR. The IVIM models were inferior to ADC and SEM at predicting pCR.
['Liang|Chun-Yi|CY|', 'Chen|Mao-Dong|MD|', 'Zhao|Xi-Xi|XX|', 'Yan|Cheng-Gong|CG|', 'Mei|Ying-Jie|YJ|', 'Xu|Yi-Kai|YK|']
D038524:Diffusion Magnetic Resonance Imaging D005260:Female D006801:Humans D008297:Male D008875:Middle Aged D008962:Models, Theoretical D020360:Neoadjuvant Therapy D011379:Prognosis D012372:ROC Curve D012004:Rectal Neoplasms D012007:Rectum D012680:Sensitivity and Specificity D016896:Treatment Outcome D047368:Tumor Burden
Multiple mathematical models Locally advanced rectal cancer Whole-tumor volume DWI Histogram analysis Response prediction