When the FDA approved Abiraterone with prednisone (Zytiga) in the pre-chemotherapy stage they approved it after an interim analysis of data was performed of the phase III clinical trial (COU-AA-302), The analysis was performed by an independent data monitoring committee that found a significant difference in radiographic progression-free survival (scans that showed no tumor progression against placebo scans that showed significant progression) and a statistical trend toward improved overall survival. Usually the FDA wants a trial to continue until actual survival statistics have been developed, but in the case of Zytiga they approved it without these final statistics.

Final results of the trial have now been calculated and support the survival benefit of Zytiga. “The study met the overall survival endpoint and all secondary endpoints with statistical as well as clinical significance,” stated Charles J. Ryan, MD, Professor of Clinical Medicine and Urology at the University of California, San Francisco, Helen Diller Family Comprehensive Cancer Center. “Despite 44% crossover from the control arm to treatment with abiraterone, the survival benefit associated with abiraterone was maintained.”

In the final overall survival analysis, the actual benefit for abiraterone appeared less robust than that suggested by progression-free survival at the interim analysis. However, after a median follow-up of 49.2 months, overall survival was significantly better for men receiving abiraterone and prednisone, with a median of 34.7 vs. 30.3 months for placebo (or a survival advantage of 4.4 months).

We now have actual survival data for Zytiga. In comparison to the survival advantage of 4.4 months with Zytiga, Xtandi demonstrated a 2.2 month advantage and Provenge a 4.1 month advantage in the similar disease stage (castrate resistant, metastatic without any chemotherapy exposure).

Ryan C, Smith M, Fizazi K, et al: Final overall survival analysis of COU-AA-302, a randomized phase 3 study of abiraterone acetate in metastatic castration-resistant prostate cancer patients without prior chemotherapy. ESMO 2014 Congress. Abstract 753O.

Disclosure: Dr. Ryan has received honoraria from Jansen

Joel T. Nowak, M.A., M.S.W.