The goal of this clinical trial is to determine whether stereotactic body radiotherapy (SBRT) delivered in five fractions is non-inferior to standard-of-care mildly hypofractionated radiotherapy in terms of patient-reported quality of life in adults with prostate cancer who require adjuvant or salvage radiotherapy after radical prostatectomy. The trial includes patients with or without a macroscopic recurrence in the prostate bed and allows irradiation of the regional lymphatic drainage when clinically indicated.
The main questions it aims to answer are:
* Is SBRT non-inferior to standard-of-care radiotherapy regarding urinary (GU) quality of life, measured by the change in the EPIC-26 GU domain score from baseline to 24 months after radiotherapy?
* Is SBRT non-inferior to standard-of-care radiotherapy regarding bowel (GI) quality of life, measured by the change in the EPIC-26 GI domain score from baseline to 24 months after radiotherapy?
Researchers will compare SBRT delivered as 6 Gy × 5 fractions to the prostate bed with standard-of-care radiotherapy delivered as 2.625 Gy × 20 fractions (total dose 52.5 Gy) to determine whether the substantially shorter SBRT treatment provides non-inferior patient-reported urinary and bowel outcomes. When clinically indicated, treatment of the lymphatic drainage and a simultaneous integrated boost to macroscopic recurrence or involved lymph nodes may also be delivered.
Participants will:
* Be randomly assigned in a 1:1 ratio to receive either five-fraction SBRT or 20-fraction standard-of-care radiotherapy.
* Receive radiotherapy to the prostate bed, with additional irradiation of the regional lymphatic drainage and/or a boost to macroscopic disease or involved lymph nodes when clinically indicated.
* Complete questionnaires assessing quality of life, urinary symptoms, and sexual function, including EPIC-26, IPSS, and IIEF-5.
* Undergo clinical assessments, PSA measurements, assessment of treatment-related adverse events, and radiological imaging when clinically indicated.
* Attend follow-up assessments at 3, 6, 12, 18, and 24 months after radiotherapy and then annually for up to 5 years.
A total of 206 participants are planned for the trial. In addition to the primary quality-of-life outcomes, researchers will assess acute and late toxicity, biochemical recurrence-free survival, progression-free survival, time to further anti-cancer therapy, prostate cancer-specific survival, and overall survival.