Multicenter phase 2 trial of nivolumab in patients with metastatic castration-resistant prostate cancer with and without DNA repair defects

A multicenter phase 2 trial in Brazil evaluated the impact of DNA repair defects (DRD) on the efficacy of nivolumab in patients with post-docetaxel patients with metastatic castration-resistant prostate cancer (mCRPC). DRD was assessed in circulating tumor DNA (ctDNA). DRD was identified in 30.5% of the patients. The overall PSA₅₀ response rate was 10.5%. PSA₅₀ response and objective response rate did not differ significantly between patients with and patients without DRD (p=0.57 and p=0.27, respectively). Median PSA-PFS (1.9 versus 2.8 months; p=0.52) and radiographic progression-free survival (3.4 versus 5.5 months; p=0.7) were not statistically different between patients with and without DRD. The authors conclude that nivolumab has clinical activity in a subset of mCRPC patients. DRD did not predict response.