ESTRO 2025 - Abstract Book

S1902

Clinical - Urology

ESTRO 2025

Conclusion: Results of our study and data from literature sources allow us to conclude that SRT in HF is an effective method in the combined treatment of patients with recurrent PCa after RP and can be considered as an alternative radiotherapy option, provided that technical capabilities and appropriate clinical experience are available.

Keywords: salvage, prostate cancer, hypofractionation

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Digital Poster MRguided prostate SBRT for prostate cancer. A single centre series of 440 consecutive patients. Shira Stern 1,2 , Michal Friedman 1,2 , Yuli Percik 1,2 , Merav A Ben David 1,2 , Svetlana Zalmanov 1,2 , Yoav Lipski 1,2 , Vlad Greenberg 1,2 , Elena Chernomordikov 1,2 , Sara Apter 1,3 , Keren Hod 1 , Raphael Pfeffer 1,2 1 Radiation Oncology, Assuta Medical Center, Tel Aviv, Israel. 2 Medical School, Ben Gurion University, BeerSheba, Israel. 3 Medical School, Tel Aviv University, Tel Aviv, Israel Purpose/Objective: To analyse safety and efficacy of MR-guided stereotactic body radiotherapy (MRgRT) in 440 consecutive patients with localized prostate cancer treated at a single centre. Minimum follow-up is 18 months . Material/Methods: Patients with localized prostate cancer referred for SBRT since 2019 received five fractions of 7.25 Gy for a total of 36.25 Gy delivered on a 0.35 Tesla MRguided linear accelerator. Since January 2020, a boost to 40 Gy was delivered based on GTV defined by a combination of biopsy proven GG2 disease, MRI and/or PET-PSMA. Prostate and GTV volumes were reviewed at a contouring conference including a radiologist expert in MRI. No spacers were used. Daily plans were adjusted if tumor or organ-at-risk (OAR) doses deviated significantly on pre treatment MRI compared to the simulation MRI. The prostate was continuously monitored during treatment, with automatic cessation if the prostate moved outside the planned treatment volume (PTV) range . Results: Mean age was 71.3 years. 98% of patients underwent 3T MRI before simulation. PIRADS 4/5 was observed in 88% of patients, 15% presented with extracapsular extension (ECE). PET-PSMA was performed in 82% of patients. Risk stratification showed 16% as low risk, 61% intermediate risk, and 23% high risk. ADT was administered to 34% of patients. The baseline PSA averaged 6.4 ng/ml, with prostate volumes ranging from 18.3 to 227.5 cc (mean 64.7 cc). The average follow-up period was 33.6 months. Biochemical failure occurred in 5.6% of patients not receiving ADT (16/285), 6 in the prostate, 2 in seminal vesicles (SV), 4 in lymph nodes (LN), 1 with metastasis, 2 with biochemical failure (BF) only, and 2 with a combination of failures. The overall failure rate in the study group was 5.3% (8 in prostate, 6 in LN, 2 with metastasis, and others/combination). The nadir PSA was significantly lower in patients without treatment failure (0.85 ng/ml) compared to those with failure (1.58 ng/ml, p=0.001). The mean PSA after 5 months was 1.9 (66% reduction) and 0.7 after 28 months. Complications included increased nocturia in 18.5%, constipation and fatigue in 15%, irritable bladder in 8%, and 1.5-2% reported new incontinence, pain, or reversible urinary retention. Conclusion: With a follow-up of 2.75 years, MRgRT is a safe and effective treatment for localized prostate cancer, demonstrating a low incidence of side effects. A PSA nadir of less than 1 ng/ml was found to be a strong indicator of favorable treatment outcomes.

Keywords: prostate, SBRT, MRguided