Reduction of dose to duodenum with a refined delineation method of Para-aortic region in patients with locally advanced cervical Cancer receiving prophylactic extended-field radiotherapy.
BACKGROUND
To compare irradiation dose to the second and third portions of duodenum (Duo2 and Duo3) with a new refined and old delineation method of para-aortic region for patients with locally advanced cervical cancer (LACC) receiving prophylactic extended-field radiotherapy (EFRT).


METHODS
Twenty consecutive patients with LACC were treated with prophylactic EFRT from January 2016 to January 2017 at our institute. Two delineation methods of para-aortic region were designed for each patient, the old delineation method ensured a full coverage of aortic and inferior vena cava, while the right paracaval region above L3 was omitted from CTV in the new delineation method. Patients received a dose of 50.4Gy in 28 fractions for PCTV and a dose of 60.2Gy in 28 fractions for PGTV with volumetric-modulated arc therapy (VMRT). The dose delivered to Duo2 and Duo3 with these two delineation methods were compared.


RESULTS
All treatment plans achieved excellent target volume coverage with 95% of PCTV receiving 50.4Gy and 95% of PGTV receiving 60.2Gy. There was no difference between delineation methods in low dose level (V5, V10, V15, V20, V25) for Duo2 and Duo3. The V30, V35, V40, V45, V50, Dmax, Dmean and D2cc for Duo2 with the new and old delineation methods were 55.76% vs 80.54% (P = 0.009), 34.72% vs 70.91% (P < 0.001), 18.69% vs 55.46% (P < 0.001), 8.20% vs 41.49% (P < 0.001), 1.86% vs 21.60% (P < 0.001), 49.58Gy vs 52.91Gy (P = 0.002), 30.38Gy vs 39.22Gy (P = 0.001) and 37.90Gy vs 48.64Gy (P < 0.001) respectively. For Duo3, the new delineation method achieved significant advantages in V30, V35, V40, V45, V50 and Dmean over the old one (96.82% vs 99.25%, P = 0.021; 89.65% vs 97.21%, P = 0.001; 79.50% vs 93.18%, P < 0.001; 65.63% vs 82.93%, P < 0.001; 43.39% vs 65.60%, P < 0.001; 46.09Gy vs 49.24Gy, P < 0.001), no deference was observed regarding D2cc and Dmax with these two delineation methods.


CONCLUSION
With the new delineation method of para-aortic area in prophylactic EFRT, significant reduction of irradiation dose to the second and third portions of duodenum in high dose area was obtained. This may further lower the incidence of duodenal toxicity when performing prophylactic EFRT for patients with LACC.
['Yang|Bo|B|', 'Liu|Xiaoliang|X|', 'Hu|Ke|K|http://orcid.org/0000-0003-1079-5137', 'Qiu|Jie|J|', 'Zhang|Fuquan|F|', 'Hou|Xiaorong|X|', 'Yan|Junfang|J|', 'Meng|Qingyu|Q|', 'Wang|Weiping|W|', 'Yu|Lang|L|', 'Wang|Yijun|Y|']
D001011:Aorta D004386:Duodenum D005260:Female D006801:Humans D009364:Neoplasm Recurrence, Local D058958:Organs at Risk D011835:Radiation Protection D011874:Radiometry D011878:Radiotherapy D011879:Radiotherapy Dosage D011880:Radiotherapy Planning, Computer-Assisted D050397:Radiotherapy, Intensity-Modulated D012189:Retrospective Studies D016896:Treatment Outcome D002583:Uterine Cervical Neoplasms
Cervical cancer Dosimetric comparison Prophylactic extended field radiotherapy Target delineation