Inclusion Criteria:  Histologically-proven prostate cancer pT1-T4 pN0/Nx cM0 PSA at BCR >0.1 - <0.3 ng/mL post-radical prostatectomy PSMA PET/CT negative at BCR post radical prostatectomy Planned SRT to prostate bed +/- pelvic lymph nodes ECOG 0 or 1 Age ≥ 18 years Informed consent: All patients must sign a document of informed consent indicating their understanding of the investigational nature and risks of the study before any protocol related studies are performed.  Exclusion Criteria:  Active or post prostatectomy androgen deprivation use Previous pelvic radiotherapy Other contraindications to radiotherapy