Surveillance or metastasis-directed Therapy for OligoMetastatic Prostate cancer recurrence (STOMP): study protocol for a randomized phase II trial

Background: Metastases-directed therapy (MDT) with surgery or stereotactic body radiotherapy (SBRT) is emerging as a new treatment option for prostate cancer (PCa) patients with a limited number of metastases (<= 3) at recurrence - so called "oligometastases". One of the goals of this approach is to delay the start of palliative androgen deprivation therapy (ADT), with its negative impact on quality of life. However, the lack of a control group, selection bias and the use of adjuvant androgen deprivation therapy prevent strong conclusions from published studies. The aim of this multicenter randomized phase II trial is to assess the impact of MTD on the start of palliative ADT compared to patients undergoing active surveillance. Methods/Design: Patients with an oligometastatic recurrence, diagnosed on choline PET/CT after local treatment with curative intent, will be randomised in a 1:1 ratio between arm A: active surveillance only and arm B: MTD followed by active surveillance. Patients will be stratified according to the location of metastasis (node vs. bone metastases) and PSA doubling time (<= 3 vs. > 3 months). Both surgery and SBRT are allowed as MDT. Active surveillance means 3-monthly PSA testing and re-imaging at PSA progression. The primary endpoint is ADT-free survival. ADT will be started in both arms at time of polymetastatic disease (>3 metastatic lesions), local progression or symptoms. The secondary endpoints include progression-free survival, quality of life, toxicity and prostate-cancer specific survival. Discussion: This is the first randomized phase 2 trial assessing the possibility of deferring palliative ADT with MDT in oligometastatic PCa recurrence.