S1204
Clinical - Urology
ESTRO 2026
without grade 3 events. Genitourinary (GU) symptoms were common, predominantly grade 1–2. By 6 weeks, GI and GU toxicity decreased markedly and remained low-grade. At late follow-up, chronic GI, GU and sexual toxicities were mostly G1-G2. Rectal D50 % was the only dosimetric factor significantly associated with acute GI events (OR = 1.09; 95 % CI 1.017–1.174; p = 0.028); D50 % > 22.9 Gy tripled the risk (OR = 3.09; p = 0.005). Penile-bulb Dmean correlated with sexual dysfunction (OR = 1.06; 95 % CI 1.023–1.097; p = 0.001), while prior transurethral resection of the prostate (TURP) increased chronic GU toxicity (OR = 3.43; p = 0.006; AUC = 0.725). bPFS did not differ across risk groups (log-rank p = 0.85).
Conclusion: The 56 Gy/14-fraction alternate-day regimen achieved excellent biochemical control with minimal toxicity. Outcomes were comparable to CHHiP and PROFIT (60 Gy/20 fr), with lower late effects than HYPRO (3.4 Gy/fr). Delivering treatment in 14 alternate-day fractions over 5 weeks reduces treatment burden while preserving tumour control and safety. This intermediate-hypofractionation schedule provides a favourable therapeutic ratio and broad efficacy across risk groups, bridging the gap between moderate and extreme hypofractionation and supporting its consideration as a standard option for localized prostate cancer. References: 1. Kountouri M, Zilli T, Rouzaud M, Dubouloz A, Linero D, Escudé L, et al. Moderate hypofractionated protracted radiation therapy and dose escalation for prostate cancer: Do dose and overall treatment time matter? Int J Radiat Oncol Biol Phys. 2016;94(2):272–9. Keywords: hypofractionation, prostate cancer, toxicity
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