Abiraterone or Enzalutamide in Advanced Castration-Resistant Prostate Cancer: An Indirect Comparison

BACKGROUND: To perform a comparative effectiveness analyses between enzalutamide and abiraterone acetate in both the pre-docetaxel and post-docetaxel settings based on published phase III randomized trials. METHODS: The primary measure of efficacy was the posterior probability that enzalutamide outperforms abiraterone acetate (AA) with prednisone in terms of overall survival (OS) on average. Indirect meta-estimates were generated from four randomized studies in the context of a Bayesian hierarchical model with study-specific efficacy estimates meta-analyzed on the log scale. RESULTS: We found weak evidence that enzalutamide outperforms AA with prednisone in terms of OS in the pre-docetaxel and post-docetaxel settings. However, we found strong evidence that enzalutamide outperforms AA with prednisone in terms of radiographic PFS, time until PSA progression, and PSA response rate in both the pre- and post-docetaxel settings. Rates of grade 3 or worse adverse events were broadly similar between treatment (enzalutamide or AA) and control arms (placebo or placebo with prednisone) in all included randomized studies. CONCLUSIONS: There is strong evidence that enzalutamide outperforms AA with prednisone in terms of radiographic PFS and PSA progression and PSA response rate but not OS in the pre and post-docetaxel settings. These results may further guide clinicians in making treatment recommendations for patients with advanced prostate cancer. Prostate 77: 639-646, 2017.