S1178
Clinical - Urology
ESTRO 2026
Results: Median follow-up was 46 months. bRFS was 87.5% at 1 year, 67.3% at 2 years, and 46.5% at 3 years (median: 33.5 months). ADT-FS was 91.4% at 1 year and 73.0% at 2 years. Acute GU grade ≥ 2 toxicity occurred in 8.8% of patients (one grade 3 event), and acute GI grade ≥ 2 toxicity in 0.8%. Late GU grade ≥ 2 toxicity occurred in 26% of patients (4.9% grade 3), with hematuria being the most frequent severe symptom. Late GI grade ≥ 2 toxicity occurred in 9% (2.4% grade 3).In univariate analysis, PSA nadir after reSBRT, PSA doubling time at recurrence, PSA at recurrence, initial ISUP grade, initial TNM stage, use of initial androgen deprivation therapy, time to PSA nadir post-reSBRT, and interval between irradiations were significantly associated with bRFS. In multivariate analysis, PSA nadir after reSBRT (HR = 2.45; 95%CI [1.65–3.63]; p < 0.00001) and PSA doubling time (HR = 0.90; 95%CI [0.86–0.95]; p = 0.0002) remained independent predictors. The pre- treatment prognostic score, including ISUP grade, initial TNM, interval between irradiations, PSA at recurrence, and PSA doubling time, stratified 24- month bRFS into low (87%), intermediate (71%), and high-risk groups (44%) (global log-rank test p < 0.000001). Incorporating post-treatment PSA nadir refined this classification to 93% (low), 78% (intermediate), and 41% (high-risk groups) (global log- rank test p < 0.000001).
and low rates of severe late toxicity. Randomised studies are needed to draw conclusions about the differences between the two techniques. References: Sanmamed N, et al. Tumor-targeted dose escalation for localized prostate cancer using MR-guided HDR brachytherapy (HDR) or integrated VMAT (IB-VMAT) boost: Dosimetry, toxicity and health related quality of life. Radiother Oncol. 2020;149:240-5.Groen VH, et al. Patterns of failure following external beam radiotherapy with or without an additional focal boost in the randomized controlled FLAME trial for localized prostate cancer. Eur Urol. 2022;82:252-257.Draulans C, et al. Stereotactic body radiotherapy with a focal boost to the intraprostatic tumor for intermediate and high risk prostate cnacer: 5-year efficacy and toxicity in the hypo-FLAME trial. Radiother Oncol. 2024;201:110568. Keywords: prostate, intraprostatic boost, HDR-VMAT Digital Poster Highlight 1257 Stereotactic re-irradiation for intraprostatic recurrences: outcomes, toxicity, and proposal of a prognostic score Yazid ABOU EL FATTAH 1 , Astrid THOMIN 1 , Thomas FREDERIC-MOREAU 2 , Gilles CALAIS 1 1 Clinique d'oncologie radiothérapie (CORAD), CHRU de TOURS, Tours, France. 2 Radiothérapie, Centre Saint- Jean, Saint-Doulchard, France Purpose/Objective: To report oncologic outcomes, toxicity, and prognostic factors in patients undergoing stereotactic body radiotherapy (reSBRT) for local prostate cancer recurrence after previous definitive radiotherapy, and to propose a prognostic score to guide clinical decision-making. Material/Methods: This retrospective single-center study included 125 patients treated with reSBRT for intraprostatic recurrence between 2013 and 2023. Recurrence was confirmed by multiparametric MRI and/or fluorocholine PET-CT, biopsy was not mandatory. Most patients received 35 Gy (30–36.25 Gy) in 5 fractions. The primary endpoint was biochemical relapse-free survival (bRFS) according to the Phoenix criteria. Secondary endpoints were androgen deprivation therapy-free survival (ADT-FS), acute and late genitourinary (GU) and gastrointestinal (GI) toxicities graded by CTCAE v5.0, and prognostic factor identification by Cox regression. A prognostic score was developed from significant pre-treatment variables and further refined by integrating post- treatment factors.
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