Dosimetry Contribution: Rectal balloon use limits vaginal displacement, rectal dose, and rectal toxicity in patients receiving IMRT for postoperative gynecological malignancies Cheng-Chia Wu, M.D., Ph.D.,* ,1 Yen-Ruh Wuu, B.S.,* ,1 Theodore Yanagihara, M.D., Ph.D.,* Ashish Jani, M.D.,* Eric P. Xanthopoulos, M.D., J.D.,* Akhil Tiwari, B.S.,* Jason D. Wright, M.D., † William M. Burke, M.D., † June Y. Hou, M.D., † Ana I. Tergas, M.D., † and Israel Deutsch, M.D.* ,‡ *Department of Radiation Oncology, Columbia University Medical Center, New York, NY; † Department of Gynecologic Oncology, Columbia University Medical Center, New York, NY; and ‡ Herbert Irving Comprehensive Cancer Center, Columbia University Medical Center, New York, NY ARTICLE INFO Article history: Received 10 November 2016 Received in revised form 20 June 2017 Accepted 25 July 2017 Keywords: Rectal balloon IMRT Endometrial Cervical Hysterectomy A B ST R AC T Pelvic radiotherapy for gynecologic malignancies traditionally used a 4-field box tech- nique. Later trials have shown the feasibility of using intensity-modulated radiotherapy (IMRT) instead. But vaginal movement between fractions is concerning when using IMRT due to greater conformality of the isodose curves to the target and the resulting possibility of missing the target while the vagina is displaced. In this study, we showed that the use of a rectal balloon during treatment can decrease vaginal displacement, limit rectal dose, and limit acute and late toxicities. Little is known regarding the use of a rectal balloon (RB) in treating patients with IMRT in the posthysterectomy setting. We hypothesize that the use of an RB during treatment can limit rectal dose and acute and long-term toxicities, as well as decrease vaginal cuff displacement between fractions. We performed a retrospective review of patients with gynecological malignancies who received postoperative IMRT with the use of an RB from January 1, 2012 to January 1, 2015. Rectal dose constraint was examined as per Radiation Therapy Oncology Group (RTOG) 1203 and 0418. Daily cone beam computed tomography (CT) was performed, and the average (avg) displacement, avg magnitude, and avg magni- tude of vector were calculated. Toxicity was reported according to RTOG acute radiation morbidity scoring criteria. Acute toxicity was defined as less than 90 days from the end of radiation treatment. Late toxicity was defined as at least 90 days after completing radia- tion. Twenty-eight patients with postoperative IMRT with the use of an RB were examined and 23 treatment plans were reviewed. The avg rectal V40 was 39.3% ± 9.0%. V30 was 1 Cheng-Chia Wu and Yen-Ruh Wuu contributed equally to this work. Reprint requests to Israel Deutsch, M.D., Department of Radiation Oncology, Columbia University Medical Center, 622 West 168th Street, BNH B011, New York, NY 10032. E-mail: id2182@cumc.columbia.edu http://dx.doi.org/10.1016/j.meddos.2017.07.011 0958-3947/Copyright © 2017 American Association of Medical Dosimetrists Medical Dosimetry ■■ (2017) ■■–■■ ARTICLE IN PRESS Medical Dosimetry journal homepage: www.meddos.org