Supriya Chopra1, Tapas Dora2, Reena Engineer3, Siji Mechanery2, Priyanka Agarwal2, Sadhna Kannan4, Yogesh Ghadi3, Jamema Swamidas3, Umesh Mahantshetty3, Shyam Kishore Shrivastava3. 1. Department of Radiation Oncology, Advanced Centre for Treatment Research and Education in Cancer, Tata Memorial Centre, Navi Mumbai, Maharashtra, India. Electronic address: schopra@actrec.gov.in. 2. Department of Radiation Oncology, Advanced Centre for Treatment Research and Education in Cancer, Tata Memorial Centre, Navi Mumbai, Maharashtra, India. 3. Department of Radiation Oncology, Tata Memorial Hospital, Tata Memorial Centre, Mumbai, Maharashtra, India. 4. Epidemiology and Clinical Trials Unit, Advanced Centre for Treatment Research and Education in Cancer, Tata Memorial Centre, Navi Mumbai, Maharashtra, India.
Abstract
PURPOSE: To investigate the correlation of rectal dose volume metrics with late rectal toxicity after high-dose-rate pelvic interstitial brachytherapy. METHODS AND MATERIALS: 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. RESULTS: 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. CONCLUSIONS: Limiting 2-cc RM and rectal doses within the proposed thresholds can minimize Grade ≥II toxicity for gynecologic high-dose-rate interstitial brachytherapy.
PURPOSE: To investigate the correlation of rectal dose volume metrics with late rectal toxicity after high-dose-rate pelvic interstitial brachytherapy. METHODS AND MATERIALS: 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. RESULTS: 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. CONCLUSIONS: Limiting 2-cc RM and rectal doses within the proposed thresholds can minimize Grade ≥II toxicity for gynecologic high-dose-rate interstitial brachytherapy.
Authors: Richard Pötter; Kari Tanderup; Christian Kirisits; Astrid de Leeuw; Kathrin Kirchheiner; Remi Nout; Li Tee Tan; Christine Haie-Meder; Umesh Mahantshetty; Barbara Segedin; Peter Hoskin; Kjersti Bruheim; Bhavana Rai; Fleur Huang; Erik Van Limbergen; Max Schmid; Nicole Nesvacil; Alina Sturdza; Lars Fokdal; Nina Boje Kibsgaard Jensen; Dietmar Georg; Marianne Assenholt; Yvette Seppenwoolde; Christel Nomden; Israel Fortin; Supriya Chopra; Uulke van der Heide; Tamara Rumpold; Jacob Christian Lindegaard; Ina Jürgenliemk-Schulz Journal: Clin Transl Radiat Oncol Date: 2018-01-11