ESTRO 2025 - Abstract Book

S2038

Clinical - Urology

ESTRO 2025

week, with urethral catheter placement during each session. The total dose administered, when combined with prior radiation, was limited to a total equivalent dose in 2 Gy (EQD2) of 100 Gy to the rectal wall and 110 Gy to the bladder and urethra. Toxicity was evaluated using the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0. Results: We collected data from 17 patients, with a median follow-up of 33 months. The median age at the time of salvage SBRT was 73.2 years, and the mean pre-treatment PSA level was 4.08 ng/mL (range 2.14 – 9.91). The median time between the initial radiotherapy and reirradiation was 9.6 years. Acute genitourinary (GU) toxicity was observed in 9 patients (52.9%), with none exceeding grade 2. One patient (5.9%) experienced acute gastrointestinal (GI) toxicity, which was grade 2. Late toxicities included GI toxicity in 3 patients (17.6%), with 2 cases (11.8%) classified as grade 3, and GU toxicity in 11 patients (64.7%), with 3 cases (17.6%) classified as grade 3. Local recurrence after reirradiation occurred in 4 patients (23.5%) with a median time of 22.8 months. The distant progression-free survival (PFS) was 82.35%, while the overall survival (OS) rate was 94%. Conclusion: SBRT reirradiation for locally recurrent prostate cancer after prior radiotherapy is a safe and feasible treatment option in selected patients, with acceptable toxicity profiles and promising clinical outcomes. Further investigation with larger cohorts is warranted to confirm these results. Digital Poster Follow-up of an "EMBARK-like" Cohort of Prostate Cancer Patients Using Molecular Imaging: A Single-Center Retrospective Analysis María Cerrolaza 1 , Agustina Méndez 1 , Victoria Navarro 2 , Cristina García 1 , Claudia Colom 1 , Ana Galán 1 , Claudia Laborda 1 , Martin Tejedor 1 1 Radiation Oncology, Miguel Servet University Hospital, Zaragoza, Spain. 2 Radiation Oncology, Lozano Blesa University Clinical Hospital, Zaragoza, Spain Purpose/Objective: In the EMBARK clinical trial, patients with high-risk biochemical recurrence (BCR) of prostate cancer who received enzalutamide plus leuprolide or enzalutamide monotherapy showed superior metastasis-free survival compared to leuprolide alone. High- risk disease was defined as a PSA doubling time (PSADT) ≤9 months and a PSA ≥2 ng/mL above nadir after radiation therapy (RT), or ≥1 ng/mL after radical prostatectomy (RP) with or without salvage radiation (SRT). Early SRT (PSA <0.5 ng/mL) has been shown to improve cancer-specific survival. Additionally, PET imaging (choline or PSMA) enhances diagnostic accuracy over conventional imaging. The aim of this study is evaluate clinical outcomes, and progression patterns in patients with BCR after radical RT and SRT after RP, using the EMBARK criteria in our center. Material/Methods: A retrospective analysis was conducted on patients with BCR at our institution, using PSA ≥ 0.4 ng/mL and PSA ≥ 2 ng/mL above nadir as recurrence criteria following SRT after RP and definitive RT, respectively. Imaging with either choline PET or PSMA PET was performed. The location of recurrence, treatment modalities, and current disease control status were analyzed. Keywords: reirradiation, SBRT, prostate 3143