S1135
Clinical - Urology
ESTRO 2026
Digital Poster 299
Propensity-matched hypofractionated versus conventional radiotherapy for prostate salvage: outcomes and safety (HyPRoST) Nicholas Kozak, Julian Kim, Arbind Dubey, Rashmi Koul, Bashir Bashir, Amitava Chowdhury, Aldrich Ong, Eric Van Uytven, Florence Mutua, Vibhay Pareek Radiation Oncology, CancerCare Manitoba, Winnipeg, Canada Purpose/Objective: HyPRoST evaluated the baseline characteristics, recurrence patterns, and adverse events of hypofractionated versus conventionally fractionated post-prostatectomy radiotherapy using propensity- matched analysis in a single-institution cohort. Material/Methods: A retrospective analysis included 428 patients treated with post-prostatectomy radiotherapy at CancerCare Manitoba from 2009 to 2023. Of these, 73 patients received hypofractionated radiotherapy (HFRT) since June 2020, while 355 received conventionally fractionated radiotherapy (CFRT). The primary endpoint was progression-free survival (PFS), defined as PSA ≥ 2 ng/mL above nadir, clinical failure (local, regional, or distant), death, or initiation of ADT for rising PSA. Secondary endpoints included overall survival (OS), metastasis-free survival (MFS), and cumulative incidence of grade 3 adverse events, which were analyzed using Kaplan-Meier estimates and log- rank tests. Adverse events were assessed per CTCAE v5.0, with additional data on clinical interventions (e.g., cystoscopy). Propensity matching included seven parameters: age, Gleason score, pathologic stage, PSA before surgery, time to recurrence, adjuvant versus salvage intent, and ADT duration. High risk disease was defined as stage pT3a or higher, pN1, pre-surgery PSA ≥ 20 ng/mL, or Gleason grade group 4 or 5. Results: Median follow-up was 2.3 years for HFRT and 5.5 years for CFRT. There were no statistically significant differences in PFS, OS, or MFS between HFRT and CFRT groups in the propensity match analysis or in the unmatched analysis. In the unmatched analysis, patients receiving HFRT had fewer positive margins (49.3% vs 62.9%, p = 0.034), a longer median interval to recurrence post-prostatectomy (32.7 vs. 20.7 months, p < 0.01), a lower median PSA before radiotherapy (0.26 vs 0.33 ng/ml, p < 0.01), and less frequently received concurrent ADT (17.8% vs. 42.0%, p < 0.01). In the matched cohorts, there were no statistically significant differences in any baseline characteristics or covariates.
The cumulative incidence of grade 3 adverse events was not statistically different between HFRT and CFRT groups (p = 0.659). In the pooled analysis, patients with high-risk disease were more likely to have progression after post-prostatectomy radiation (p < 0.01). Patients who exceeded both dose guidances for the bladder were more likely to have grade 3 adverse urinary events than those who did not (50.0% vs 12.9%, p < 0.01).
Conclusion: To our knowledge, this is the largest propensity- matched analysis evaluating hypofractionated post- prostatectomy radiotherapy at a single institution. HyPRoST indicates that HFRT provides efficacy and safety comparable to CFRT. These results endorse HFRT as a feasible treatment option, meriting further prospective investigations. References: 1. Buyyounouski MK, Pugh SL, Chen RC, Mann MJ, Kudchadker RJ, Konski AA, et al. Noninferiority of Hypofractionated vs Conventional Postprostatectomy Radiotherapy for Genitourinary and Gastrointestinal
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