Oligometastatic prostate cancer: stereotactic ablative radiotherapy is effective and safe

  • Phillips R & et al.
  • JAMA Oncol
  • 26 Mar 2020

  • curated by Deepa Koli
  • Univadis Clinical Summaries
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Takeaway

  • 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.

Study design

  • 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.

Key results

  • 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).

Limitations

  • Findings need validation in phase 3 trial.