ESTRO 2025 - Abstract Book

S2077

Clinical - Urology

ESTRO 2025

Conclusion: Salvage SBRT to the prostate bed demonstrated excellent safety, minimal severe toxicity, and promising biochemical control. Long-term follow-up and randomized comparisons with different RT schedules are needed to validate this approach.

Keywords: SBRT, prostate cancer, salvage radiotherapy

3898

Digital Poster One-day urethral-sparing, HDR-like, prostate cancer robotic SBRT: preliminary results of the PRO-FAST trial Andrei Fodor 1 , Laura Giannini 1 , Sara Broggi 2 , Miriam Torrisi 1 , Paola Mangili 2 , Andrea Losa 3 , Tommaso Maga 3 , Roberta Tummineri 1 , Chiara Lucrezia Deantoni 1 , Alessia Tudda 2 , Lucia Perna 2 , Roberta Castriconi 2 , Paolo Passoni 1 , Carmen Gigliotti 2 , Cesare Cozzarini 1 , Claudio Fiorino 2 , Franco Gaboardi 3 , Antonella Del Vecchio 2 , Nadia Gisella Di Muzio 1,4 1 Radiation Oncology, IRCCS San Raffaele Scientific Institute, Milan, Italy. 2 Medical Physics, IRCCS San Raffaele Scientific Institute, Milan, Italy. 3 Urology, IRCCS San Raffaele Scientific Institute, Milan, Italy. 4 Medicine, Vita-Salute San Raffaele, Milan, Italy Purpose/Objective: Several published studies have investigated the ultrahypofractionation in single fraction for protate cancer (PCa) (1,2,3). Here we report the preliminary results of the PRO-FAST study (NCT05936736), of one-day urethral-sparing (US), HDR-like, radical robotic stereotactic body radiotherapy (SBRT) for PCa. Material/Methods: The institutional ethics commitee approved an interventional prospective single-arm trial of US-HDR-like SBRT for PCa patients. According to the optimal design of Simon, 13 patients will be enrolled for the first phase of the study. The study will be interrupted if ≥2 ≥G3 toxicities are recorded within one month from the end of SBRT, otherwise the study will continue with the second phase enrolling another 52 pts for a total of 65 pts. Five additional patients will be enrolled to compensate for any drop-offs. Primary objective is acute toxicity at one month, while secondary objectives include biochemical relapse-free-, clinical relapse-free-, cancer-specific- and overall-survival, and quality of life (assessed with quality of life questionnaires EORTC QLQ C30 and PR25, IIEF-5, IPSS, and EPIC-26). Patients with limited disease to the prostate, assessed with prostate specific membrane antigen (PSMA) positron emission tomography/computed tomography (PET/CT) (for unfavorable intermediate (UIR) and high-risk (HR) tumors) will be included. Acceptable uroflowmetry, no previous pelvic radiotherapy and relevant comorbidities are required. Importantly, all procedures are performed in just one day. The patient begins in the morning with the implantation of the 4 fiducials necessary for tracking, then performs in succession (with an urinary catheter inserted) the CT scan, MRI, contouring, planning, quality assurance control, and the delivery of the treatment, to a total dose of 24 Gy/1 fraction prescribed at the 50% isodose (with particular focus on sparing the urethra and rectal mucosa) (See example in Fig.1). Androgen deprivation is prescribed for 6 months for UIR and 2 years for HR patients. Short-term steroids and alpha lytics are admitted, for prophylactic purposes.