Background
Phase II RCT (STOMP). 62 patients with oligometastatic prostate cancer recurrence (PSA-rising, castration-sensitive, 1–3 extracranial metastases on choline PET-CT) after definitive local therapy. Randomized to surveillance (observation, no systemic therapy) vs metastasis-directed therapy (MDT: SBRT or surgery) to all metastatic lesions. Evaluated whether MDT could delay initiation of ADT.
Interventions and follow up
Arm A: MDT: SBRT (50 Gy/10 fractions or 30 Gy/3 fractions) or surgical resection to all choline PET-positive lesions (N=30)
Arm B: Surveillance: watchful waiting without systemic therapy (N=32)
Primary endpoint: ADT-free survival
mFollow up: 3.0 year
Arm B: Surveillance: watchful waiting without systemic therapy (N=32)
Primary endpoint: ADT-free survival
mFollow up: 3.0 year
Results
mADT-free survival (MDT): 21 months vs surveillance 13 months, HR 0.60, P=.11
3-yr ADT-free survival: 33% (MDT) vs 15% (surveillance)
mPFS: 21 months (MDT) vs 13 months (surveillance)
3-yr ADT-free survival: 33% (MDT) vs 15% (surveillance)
mPFS: 21 months (MDT) vs 13 months (surveillance)
Adverse events
Main adverse events: MDT arm: grade ≥2 toxicity 6.7% — vertebral fracture 1, nausea/vomiting 1. No grade ≥3 adverse events. No treatment-related deaths. QoL: similar between arms during surveillance; MDT did not reduce QoL.
Conclusions
MDT with SBRT or surgery to oligometastatic prostate cancer lesions showed a trend toward prolonging ADT-free survival (8-month delay) without reaching statistical significance in this underpowered phase II trial. The treatment was safe and did not compromise quality of life.
Key Limitations
Key Limitations: Underpowered for the primary endpoint (P=.11 not significant). Choline PET-CT is less sensitive than PSMA PET — some patients likely had undetected systemic disease. ADT-free survival is a surrogate endpoint, not OS. Small sample size limits generalizability. The STOMP update (JCO 2020) showed durable ADT-free benefit at longer follow-up.
Clinical Context
STOMP and ORIOLE together support MDT as a strategy to defer ADT initiation in oligometastatic hormone-sensitive prostate cancer. Current practice at most centers: SBRT to all PSMA PET-positive oligometastatic sites in PSA-recurrent patients to delay ADT, with shared decision-making. Phase III PEACE V/STORM trial is confirmatory.
References
References: Ost P et al, JCO 2018 (STOMP); PMID: 29240541