Phase II Trial of PSA Response-based Androgen Deprivation Therapy and Nodal Coverage for Prostate Cancer Early Salvage Radiotherapy (RANGER)

After radical prostatectomy, many men experience biochemical recurrence despite having no visible metastatic disease. Standard salvage radiotherapy is effective but often includes universal use of androgen deprivation therapy and pelvic nodal radiotherapy, which may expose many patients to unnecessary toxicity. The study evaluates a response adapted strategy using hypo fractionated or ultra hypo fractionated prostate fossa radiotherapy delivered on the Ethos adaptive radiotherapy platform. All participants will undergo 5 fractions of prostate fossa radiotherapy. At 5 weeks from treatment initiation, biochemical response will be defined as PSA \<0.05 ng/mL or a 0.2 ng/mL decrease from pre-treatment PSA. Responders will undergo observation. Non responders will receive sequential pelvic nodal stereotactic radiotherapy in 5 fractions and a 4 month course of ADT. Primary objective is to determine whether PSAA response adapted escalation achieves non inferior 2 year freedom from progression compared with historical control data. Secondary outcomes include patient reported hormonal, urinary, and bowel symptoms (EPIC-26), as well as physician graded gastrointestinal and genitourinary toxicities. Exploratory objectives include evaluating locoregional and distant failure. This approach may reduce unnecessary toxicity for responders whole allowing early selective intensification for non responders, shortening total treatment duration for all patients.