Salvage Ultrahypofractionated Postoperative External Radiotherapy For Biochemical Recurrence

Inclusion Criteria: * Subjects of male sex ≥ 18 years of age. * Subjects have freely signed the pertinent informed consent before the beginning of the study * Adenocarcinoma of the prostate treated with radical prostatectomy (any type of radical prostatectomy is permitted including retropubic, perineal, laparoscopic or robotically assisted; there is no time limit for the date of radical prostatectomy) * Detectable post-prostatectomy PSA of ≥ 0.1 - \< 2.0 ng/mL either (1) persistently detectable post-operatively or (2) developing biochemical recurrence after prostatectomy (initially undetectable) * No evidence of N1 and/or M1 disease assessed by PSMA PET-CT within 90 days prior to registration * Negative Magnetic Resonance Imaging (MRI) of the pelvis in case of equivocal evidence of local relapse on PSMA PET-CT * Androgen deprivation therapy (ADT) allowed as per physician's discretion * ECOG performance status of 0-1 * Ability to complete the questionnaires Exclusion Criteria: * N1 and or M1 patients * Macroscopic local relapse at pelvic MRI. * Prior radiation of any kind to the prostate gland or pelvis * Prior brachytherapy * History of inflammatory colitis or other active severe comorbidities * Patients who are on immunosuppressant medication