- Stereotactic ablative radiotherapy (SABR) is safe and delays progression in patients with oligometastatic prostate cancer vs observation.
- Complete consolidation of metastatic disease detectable by molecular imaging decreases the risk for subsequent metastases.
- SABR induces a systemic immune response.
Why this matters
- SABR appears to an effective metastasis-directed treatment in this setting.
- Baseline immune phenotype and tumor mutation status may predict the benefit from SABR.
- Phase 2 randomized Observation vs Stereotactic Ablative Radiation for Oligometastatic Prostate Cancer (ORIOLE) study.
- 54 patients with recurrent hormone-sensitive oligometastatic prostate cancer were randomly assigned 2:1 to receive SABR or observation.
- Funding: Nesbitt-McMaster Foundation; others.
- At 6 months, progression was reported in 19% of patients receiving SABR and 61% of those undergoing observation (P=.005).
- Disease progression rate: 11% vs 50% (P=.005).
- Median PFS: not reached vs 5.8 months (HR, 0.30; P=.002).
- Total consolidation of prostate-specific membrane antigen radiotracer-avid disease decreased the risk of new metastatic lesions at 6 months (15.8% vs 62.5%; P=.006).
- No grade ≥3 adverse events were observed.
- T-cell receptor sequencing identified significant increased clonotypic expansion following SABR.
- Greater baseline clonality was associated with progression with SABR only (0.082085 vs 0.026051; P=.03), but not with observation (P=.68).
- Findings need validation in phase 3 trial.