ESTRO 2023 - Abstract Book

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ESTRO 2023

Results Three-hundred-eighty-one patients were enrolled. Acute GI and GU G3 toxicity rates were 0.5% and 1.3%, respectively. Median EQD2 to the prostate bed ( α / β =1.5) was 71.4 Gy. Most patients (75.4%) were treated with IMRT/VMAT techniques. No patient showed G>3 acute toxicity. At multivariable logistic regression only younger age (< 65 years) was significantly correlated with increased acute toxicity (both GI and GU). Five-year GI and GU grade ≥ 3 late toxicity-free survival was 98.1% and 94.5%, respectively. The only significant correlation at Cox’s regression model was in terms of reduced risk of GI toxicity in patients undergoing hypofractionation (HR: 0.38; 95%CI: 0.18-0.78; p: 0.008) Conclusion "Modern" postoperative radiotherapy is safe, both in terms of acute and late effects, also in subjects undergoing hypofractionated regimens and especially in elderly patients. A. Montero 1 , K. Rossi 2 , O. Hernando 2 , M. Lopez 2 , J. Valero 2 , C. Cañadillas 2 , X. Chen-Zhao 2 , R. Ciervide 2 , M. Garcia-Aranda 2 , B. Alvarez 2 , A. Prado 3 , R. Alonso 2 , E. Sanchez 2 , M. Izquierdo 2 , P. Fernandez-Leton 3 , C. Rubio 2 1 HM HOSPITALES, Radiation Oncology, Madrid, Spain; 2 HM Hospitales, Radiation Oncology, Madrid, Spain; 3 HM Hospitales, Medical Physics, Madrid, Spain Purpose or Objective To evaluate feasibility and tolerance of ultra-hypofractionated (UHF) urethra-sparing SABR in a prospective cohort of high risk prostate cancer patients Materials and Methods From March 2020 to May 2022, 54p with a median age of 76-yo (52-88) were include in this prospective phase II trial. Patients’ characteristics are detailed in table 1. All patients underwent VMAT up to a total dose of 40Gy in 5 fractions of 8Gy on every other day (EQD21.5Gy = 109Gy, BED1.5Gy = 253.3Gy) with an urethra-sparing protocol that reduced prescribed dose per fraction to the urethra and the surrounding transitional zone from 8 Gy to 7.2 Gy; 24p (44%) underwent elective nodal pelvic irradiation up to a median dose of 26 Gy in 5 fractions (EQD21.5Gy = 49.8Gy) and 10p (18.5%) with macroscopical pelvic nodal disease received simultaneous integrated boost up to 40 Gy in 5 fractions (Fig.1 shows planning and dose-constraints). All patients underwent an image-guided-radiotherapy (IGRT) protocol: 33p (61%) with daily cone-beam-CT for positioning and ExacTrac system based upon prostate gold-fiducial markers for intrafraction control, and 21p (39%) by Clarity-4D Monitoring system. Daily immobilization with an endorectal balloon filled-up with 80-100cc air to minimize rectal movements was used. All patients received androgenic deprivation therapy (ADT): 52p for 24 months and 2p for 18 months.Finally, all patients were pre-medicated with alpha-1 receptor antagonist before, during and up to one month after completing SBRT. Acute a late toxicity were assessed according to RTOG/EORTC and CTCAE v5.0 criteria at one month after the end of SABR every three months during first two years every or six months thereafter and according to in-house follow-up program. PO-1475 Ultra-hypofractionated SABR in High risk prostate cancer: preliminary results of a phase II trial

Results With a median follow-up of 17.8 months (1-43) 98.1% patients are alive and 1p (1.9%) died for non-cancer cause; no patients developed biochemical progression and no distant relapses were observed.