Prostate cancer: PSA before salvage radiotherapy predicts bicalutamide response

  • Dess RT & al.
  • JAMA Oncol
  • 26 Mar 2020

  • curated by Deepa Koli
  • Univadis Clinical Summaries
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Takeaway

  • PSA levels >1.5 ng/mL before salvage radiotherapy (SRT) are significantly associated with OS benefit from bicalutamide in biochemically recurrent prostate cancer.

Why this matters

  • Pre-SRT PSA can serve as a prognostic and a predictive biomarker for hormone therapy use with SRT.

Study design

  • Secondary analysis of a double-blind phase 3 RTOG 9601 study.
  • 760 patients with recurrent prostate who had PSA elevation after radical prostatectomy were randomly assigned to either SRT+bicalutamide or placebo.
  • Funding: Prostate Cancer Foundation (DES).

Key results

  • Median follow up, 13 years.
  • In men with pre-SRT PSA levels ≥1.5 ng/mL, bicalutamide vs placebo was associated with:
    • Improved OS:
      • 12-year absolute benefit, 25% (HR, 0.45; P=.01).
    • Lower distant metastasis (subdistribution HR [sHR], 0.67; P=.03).
  • Bicalutamide did not improve OS in the pre-SRT PSA ≤1.5 ng/mL group (P=.36).
  • Early SRT (pre-SRT PSA 0.2-0.6 ng/mL):
    • No significant between-group OS difference (HR, 1.16; P=.46).
    • Higher other-cause mortality with bicalutamide (sHR, 1.94; P=.01).
  • Late SRT (pre-SRT PSA: 0.61-1.5 ng/mL):
    • OS significantly improved with bicalutamide (HR, 0.61; P=.02).
  • Risk for grade 3-5 cardiac and neurologic adverse events significantly increased with bicalutamide (OR, 2.48; P=.02).
    • Pre-SRT PSA of ≥1.5 ng/mL: OR, 2.96 (P=.02).
    • Early SRT subgroup: OR, 3.57 (P=.05).

Limitations

  • Subgroup analyses possibly underpowered.