Abiraterone acetate for metastatic castration-resistant prostate cancer after docetaxel failure: A randomized, double-blind, placebo-controlled phase 3 bridging study

Abstract

Objectives: To evaluate the efficacy and safety of abiraterone acetate-prednisone versus placebo-prednisone in Asian metastatic castration-resistant prostate cancer patients who have failed docetaxel-based chemotherapy. Methods: In this double-blind, phase 3 study from China, 214 patients were randomized (2:1) to abiraterone acetate 1000 mg once daily plus prednisone 5 mg twice daily and placebo plus prednisone 5 mg twice daily in 28-day treatment cycles. Results: Abiraterone acetate-prednisone treatment significantly decreased prostate-specific antigen progression risk by 49%, with longer median time to prostate-specific antigen progression of 5.55 months versus 2.76 months in the placebo-prednisone group (hazard ratio 0.506, P = 0.0001, primary end-point). There was a strong trend for improved overall survival in the abiraterone acetate-prednisone group, with a 40% decrease in the risk of death (hazard ratio 0.604, P = 0.0597); however, median survival was not reached in either group because of the short follow-up period (12.9 months) and limited number of observed death events. The prostate-specific antigen response rate was higher in the abiraterone-prednisone group (49.7%) than in the placebo-prednisone group (14.1%). A total of 37.1% patients in this group had pain progression events compared with 50.7% in the placebo-prednisone group. Abiraterone-prednisone significantly decreased the risk of pain progression by 50% (hazard ratio 0.496, P = 0.0014). The incidence of adverse events was similar between the two groups; the most common adverse events being anemia (25.9% for abiraterone-prednisone vs 22.5% for placebo-prednisone), hypokalemia (25.9% and 11.3%), bone pain (23.8% and 21.1%), hypertension (16.1% and 12.7%) and increased aspartate aminotransferase (14.7% and 15.5%), respectively. Conclusions: Abiraterone-prednisone significantly delays disease and pain progression, and prostate-specific antigen, with a favorable benefit-risk ratio in Asian metastatic castration-resistant prostate cancer patients in the post-docetaxel setting.