ESTRO 2025 - Abstract Book

S1996

Clinical - Urology

ESTRO 2025

Results: At a median follow-up time of 39 months (range: 1-69) 41 deaths occurred. The 4-year BRFS, CRFS, RFS, DSS, and OS in the whole population were 89%, 94%, 88%, 98%, and 81% respectively. The 4-year outcome for HR vs VHR patients compared were the following: BRFS: 92% vs 86% (p=0,012), CRFS 95% vs 91% (p=0,003), RFS 92% vs 84% (p=0,006), DSS 98% vs 99% (p=0,99), OS 87% vs 76% (p=0,08). Acute grade 2 and grade 3 UG side effects were observed in 41% and 1%, late grade 2 and grade 3 UG side effects occurred in 9.5% and 2.7% respectively. Acute and late grade 2 GI side effects were observed in 3% and 0.8% of cases. No grade 3 GI side effects were reported. Conclusion: Patients with HR and VHR prostate cancer treated with stereotactic irradiation on CK achieved favorable outcomes, with low rate of acute and late UG and GI toxicities. Omitting pelvic radiation appears to be an acceptable compromise in elderly or comorbid patients. Stereotactic extreme hypofractionated radiotherapy represents a promising, well tolerated alternative treatment in these patients.

Keywords: CyberKnife, hypofractionation, high-risk prostate

2347

Digital Poster Prostate reirradiation with online daily-adaptive stereotactic body radiotherapy (SBRT) on 1.5T MR-linac Luca Nicosia 1 , Andrea Romei 1 , Michele Rigo 1 , Andrea Gaetano Allegra 1 , Chiara De-Colle 1 , Niccolò Giaj-Levra 1 , Carolina Orsatti 1 , Edoardo Pastorello 1 , Francesco Ricchetti 1 , Ruggiero Ruggeri 1 , Filippo Alongi 1,2 1 Department of Advanced Radiation Oncology, IRCCS Sacro Cuore Don Calabria, Negrar di Valpolicella, Italy. 2 University of Brescia, University of Brescia, Brescia, Italy Purpose/Objective: Prostate re-irradiation is an attractive treatment option in the case of local relapse after previous radiotherapy, either in the definitive or in the post-operative setting. In this scenario, the introduction of MR-linacs may represent a helpful tool to improve the accuracy and precision of the treatment. Material/Methods: Patients with exclusive local relapse to the prostate or the prostate bed after primary RT were treated with a second course of SBRT on 1.5T MRL. The clinical target volume (CTV) was represented by the entire prostate gland in non operated patients or the macroscopic relapse to the prostatic bed in operated patients. In those last cases, the target was identified by the combination of MRI and PET-TC. Disease relapse was defined according to the Phoenix criteria and diagnostic imaging was requested in all patients. No confirmatory biopsy was performed due to technical difficulties of patients’ refusal for invasive procedures. The CTV was expanded by 5 mm in all direction to obtain the corresponding planning target volume (PTV). Planning mandatory goals for the urethra, the bladder and the rectum were V30Gy <1 cc. Results: 46 patients were treated with re-SBRT with the dose of 30 Gy in 5 fractions daily (10) or every-other-day (40). The median follow-up was 14 months (range 6-56). Primary RT was: conventionally fractionated RT (56.5%), prostate bed salvage RT after surgery (28.5%), SBRT (8.5%), brachytherapy (6.5%). Initial Gleason score was: 3+3 (19.5%), 3+4 (32.5%), 4+3 (15%), 4+4 or higher (19.5%), unknown (13.5%) The median time to local relapse was 76 months (range 11-189). The median IPSS at recurrence was 4 (range 0-10). All patients were staged with PET-TC PSMA (44) or choline (2). Worst acute GU toxicity was: G1 (32.5%), G2 (8.5%), G3 (2%). Worst acute GI toxicity was: G1 (35.5%). At the median follow-up only one patient had further intraprostatic relapse for wich androgen deprivation therapy (ADT) was initiated.