Safety and efficacy of moderately hypofractionated radiotherapy after radical prostatectomy: A phase II trial

BACKGROUND AND PURPOSE: This single-arm phase II study evaluated the safety and efficacy of moderately hypofractionated radiotherapy (RT) after radical prostatectomy (RP) for prostate cancer in the adjuvant or salvage setting. MATERIALS AND METHODS: Eligible patients were men aged ≥ 20 years who had undergone RP and were scheduled for adjuvant or salvage RT, with an Eastern Cooperative Oncology Group performance status of 0-2 and no prior pelvic RT or distant metastasis. RT consisted of 54 Gy in 18 fractions delivered with volumetric modulated arc therapy to the prostate bed, with optional pelvic lymph nodal bed irradiation. The primary endpoint was the incidence of grade ≥ 2 acute genitourinary (GU) and gastrointestinal (GI) toxicity. Secondary endpoints included biochemical recurrence-free survival (bRFS), toxicity, and quality of life (QoL). RESULTS: Between December 2018 and November 2021, 55 patients received protocol treatment. The median follow-up was 37.3 months. Salvage RT was performed in 49 patients (89%) and adjuvant RT in six (11%); 53% received concurrent androgen deprivation therapy. Grade ≥ 2 acute GU and GI toxicities occurred in 5.5% and 34.5% of patients, respectively; GI events were predominantly grade 2, with one patient (1.8%) experiencing grade 3 small bowel obstruction. During the relatively short follow-up period (median, 37.3 months), grade ≥ 2 late GU and GI toxicities were observed in 14.6% and 21.8% of patients, respectively. The 3-year bRFS was 65.8% (95% confidence interval, 51.1-77.1). QoL was largely maintained, with transient bowel symptoms resolving within three months. CONCLUSION: Moderately hypofractionated RT of 54 Gy in 18 fractions after RP achieved favorable biochemical control with generally manageable toxicity, supporting its feasibility.