ESTRO 2022 - Abstract Book

S1163

Abstract book

ESTRO 2022

Results All fractions were delivered at the MR-linac and it was feasible to obtain the actual delivered dose of the previous fractions before the subsequent fractions and take this into account in the online plan optimization process. Based on the accumulated dose, in 14 out of the 20 patients the online optimization goals were manually adjusted. In 3 out of the 20 patients a new reference plan was created for the remaining fractions. This was performed when the OAR constraints during beam-on were largely exceeded due to intrafraction motion. Conclusion A novel dose-adaptive workflow based on the actual delivered dose of the target volume and OARs in previous fractions is feasible for ultra-hypofractionated radiotherapy with an iso-toxic focal boost. Future studies should focus on automatization and artificial intelligence solutions to allow for rapid online dose-adaptive workflows. A. Sanchez Galvan 1 , A. Fodor 1 , C. Fiorino 2 , P. Mangilli 2 , C.L. Deantoni 1 , C. Cozzarini 1 , R. Tummineri 1 , S. Baroni 1 , S.L. Villa 1 , G. Mandurino 1 , P. Pacifico 1 , S. Arcangeli 3 , N.G. Di Muzio 4,5 1 IRCCS San Raffaele Scientific Institute, Radiotherapy, Milan, Italy; 2 IRCCS San Raffaele Scientific Institute, Medical Physics, Milan, Italy; 3 University of Milano-Bicocca, Radiotherapy, Monza, Italy; 4 IRCCS San Raffaele Scientific Institute, Radiotherapy, Milan, Italy; 5 Vita-Salute San Raffaele University, Radiotherapy, Milan, Italy Purpose or Objective Ultrahyprofractionation (UHF, SBRT) is a treatment option for patients with prostate cancer (PCa), with clinical and health- related quality-of-life (QOL) outcomes comparable to standard fractionation. The goal of this analysis is to evaluate outcomes and toxicity after an initial experience with robotic SBRT (CyberKnife, Accuray, Sunnyvale, CA, USA). Materials and Methods Between 10/2017-05/2021 102 patients with PCa were treated using a robotic SBRT. For pts characteristics see table 1. Fiducial markers were implanted into the prostate in all pts. In 52% of pts a steroid therapy and/or alpha-lytics was prescribed to prevent side effects. EORTC Quality of Life Questionnaire - Prostate Cancer Module (EORTC QLQ-PR25) and International Prostate Symptom Score (IPSS) toxicity data were recorded in pts who agreed to respond. Toxicity was scored in accordance with CTCAE v 5.0. Biochemical failure was assessed using the nadir + 2 ng/ml definition. PO-1372 Robotic stereotactic body radiotherapy for prostate cancer : an initial monoistitutional experience.