Radical prostatectomy (RP) is the most common curative approach offered to men with newly diagnosed prostate cancer. Unfortunately, up to half of these patients will have factors placing them at high risk of their cancer recurring. Having radiotherapy after RP is known to improve cure rates, but what is not known is whether it should be given straight after the operation or only when there is a rising PSA after surgery indicating active cancer. Immediate RT may not benefit all men, and can cause serious side effects such as bladder and bowel problems and impotence. International lack of consensus on the optimal timing of RT has resulted in varied clinical practice. This phase 3 trial will compare the two approaches.

This is a prospective, multi-centre, international, randomised controlled trial with a 1:1 allocation ratio. Patients with positive margins and/or pT3 disease will be randomised to adjuvant RT (Standard Arm) or active surveillance with salvage RT delivered at early relapse (Experimental Arm). 64 Gy in 32 fractions will be delivered to the prostate bed. QoL self-assessment questionnaires, Hospital Anxiety and Depression Score and toxicity will be assessed at baseline, the end of RT and annually for 5 years. Patients will be seen by their doctor 6 monthly for the first 5 years, then annually for the next 5 years. A blood test measuring prostate specific antigen (PSA) is done 3 monthly for the first 5 years for patients randomised to early salvage RT, then 6 monthly from years 5 to 10.

Inclusion Criteria:

• Prior Radical Prostatectomy (RP) for adenocarcinoma of the prostate.
• Histological confirmation of adenocarcinoma of the prostate with the Gleason score reported (Radical Prostatectomy specimen).
• Patients must have at least one of the following risk factors: 1) Positive margins, 2) Extraprostatic extension (EPE) with or without seminal vesicle involvement (pT3a or pT3b)
• Capable of starting RT within 4 months of RP (a requirement if randomised to adjuvant RT arm)
• Most recent PSA ≤ 0.10 ng/ml following RP and prior to randomisation
• Eastern Cooperative Oncology Group (ECOG) performance status 0 - 1
• Patient able to adhere to the specified follow-up schedule and complete the Quality of Life and anxiety/depression self-assessments
• Written informed consent obtained prior to randomisation
• Completion of all pre-treatment evaluations
• 18 years and older

Exclusion Criteria:

• Previous pelvic RT
• Androgen deprivation (AD) prior to or following RP
• Evidence of nodal or distant metastases
• Co-morbidities that would interfere with the completion of treatment and/or 5 years of follow-up
• Concurrent cytotoxic medication
• Hip prosthesis