COU-AA-302: Abiraterone in Pre-Chemo CRPC

The COU-AA-302 phase III trial evaluated the use of abiraterone in individuals with castration-resistant prostate cancer (CRPC) who had not received chemotherapy. From April 2009 to June 2010, 1088 patients were randomized to receive abiraterone with prednisone or prednisone with placebo. Initial outcomes data on progression-free survival were released in 2012, but mature survival data was not achieved until mid-2015, states Charles J. Ryan, MD.

During the time of this study, abiraterone was approved and became available in most countries participating in the clinical trial. As a result, 44% of patients who were initially enrolled in the placebo arm eventually received abiraterone, contributing to a large abiraterone crossover effect, notes Ryan. Median survival for men treated with abiraterone was approximately 35 months, compared with 30 months for patients who initially received prednisone and placebo (P = .0033).

There was also a significant amount of subsequent therapy with docetaxel, cabazitaxel, and enzalutamide in both arms of the study, explains Ryan. This resulted in survival curves that required a relatively long period of time to fully mature, which explains why the 2012 data did not demonstrate statistically significant endpoints while the 2015 follow-up analyses confirm significance.