Chopra Supriya, Dora Tapas, Engineer Reena, Mechanery Siji, Agarwal Priyanka, Kannan Sadhna, Ghadi Yogesh, Swamidas Jamema, Mahantshetty Umesh, Shrivastava Shyam Kishore
Department of Radiation Oncology, Advanced Centre for Treatment Research and Education in Cancer, Tata Memorial Centre, Navi Mumbai, Maharashtra, India.
Department of Radiation Oncology, Advanced Centre for Treatment Research and Education in Cancer, Tata Memorial Centre, Navi Mumbai, Maharashtra, India.
Brachytherapy. 2015 Nov-Dec;14(6):881-8. doi: 10.1016/j.brachy.2015.08.007. Epub 2015 Sep 26.
To investigate the correlation of rectal dose volume metrics with late rectal toxicity after high-dose-rate pelvic interstitial brachytherapy.
From October 2009 to November 2012, 50 patients with residual or recurrent cervical cancer were included. Patients received external radiation 50 Gy in 25 fractions over 5 weeks with weekly cisplatin. Rectum and rectal mucosal (RM) contours were delineated retrospectively. RM was defined as the outer surface of the flatus tube inserted at brachytherapy. The dose received by 0.1, 1, 2, 5 cc of rectum, RM, and sigmoid was recorded. Cumulative equivalent dose in 2 Gy (EQD2) for organs at risk was calculated assuming α/β of 3. Univariate analysis was performed to identify predictors of rectal toxicity.
At a median follow-up of 34 months (12-51 months), Grade II and III late rectal toxicity was observed in 9 (18%) and 2 (4%) patients, respectively. On univariate analysis, rectal doses were not significant predictors; however, D 0.1-cc RM dose >72 Gy (p = 0.04), D 1-cc RM dose >65 Gy (p = 0.004), D 2-cc RM dose >62.3 Gy (p = 0.004), and D 5-cc RM dose >60 Gy (p = 0.007) correlated with Grade ≥II toxicity. On probit analysis, the estimated dose in EQD2 for a 10% and 20% risk of rectal toxicity was D 2-cc rectum of 55 and 66 Gy, and RM <55 and 63 Gy, respectively.
Limiting 2-cc RM and rectal doses within the proposed thresholds can minimize Grade ≥II toxicity for gynecologic high-dose-rate interstitial brachytherapy.
探讨高剂量率盆腔组织间插植近距离放疗后直肠剂量体积指标与直肠晚期毒性反应的相关性。
纳入2009年10月至2012年11月期间50例残留或复发宫颈癌患者。患者接受5周内25次分割、每次50 Gy的外照射，并每周给予顺铂。回顾性勾画直肠及直肠黏膜（RM）轮廓。RM定义为近距离放疗时插入的肛管外表面。记录直肠、RM及乙状结肠0.1、1、2、5 cc体积所接受的剂量。假定α/β为3，计算危及器官的2 Gy等效剂量累积值（EQD2）。进行单因素分析以确定直肠毒性反应的预测因素。
中位随访34个月（12 - 51个月），分别有9例（18%）和2例（4%）患者出现II级和III级直肠晚期毒性反应。单因素分析显示，直肠剂量不是显著的预测因素；然而，RM的D0.1-cc剂量>72 Gy（p = 0.04）、D1-cc剂量>65 Gy（p = 0.004）、D2-cc剂量>62.3 Gy（p = 0.004）以及D5-cc剂量>60 Gy（p = 0.007）与≥II级毒性反应相关。经概率分析，直肠毒性反应风险为10%和20%时，EQD2中估计的直肠2-cc剂量分别为55 Gy和66 Gy，RM分别为<55 Gy和63 Gy。
将2-cc RM和直肠剂量限制在建议阈值内，可使妇科高剂量率组织间插植近距离放疗的≥II级毒性反应降至最低。
