The investigators will randomize patients presenting with early BCR with a negative baseline PSMA PET/CT, to upfront SRT or surveillance. Early BCR is defined as a PSA relapse of >0.1 to <0.3 ng/mL. Patients in the surveillance arm will be monitored with PSA every 3 months. A repeat PSMA PET/CT will be undertaken when the PSA reaches a target level of >0.5 to <1.0 ng/mL. Both early radiation treatment and surveillance with repeat PSMA PET/CT imaging are within patterns of practice locally; therefore, the investigators believe that there is clinical equipoise on this subject.

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