A single-center experience with abiraterone as treatment for metastatic castration-resistant prostate cancer

Continuous stimulation of the androgen receptor (AR) axis is a prerequisite for growth in castration-resistant prostate cancer (CRPC). Abiraterone acetate (AA) is a potent inhibitor of extracellular and intracellular androgen synthesis by inhibition of the CYP-17 enzyme system, which has been shown to be up-regulated in CRPC. AA was recently introduced in the management of patients with metastatic CRPC (mCRPC) both before and after taxane-based chemotherapy. The purpose of this study is to report the initial clinical experience obtained from mCRPC patients managed on AA at Rigshospitalet, Denmark, and compare the results with phase III trial outcomes.

Single-centre, retrospective study including consecutive patients managed on AA for more than 2-year period. Treatment consisted of 1,000mg AA and 5mg prednisone twice daily. Outcomes of interest were prostate-specific antigen (PSA) response, clinical and radiological progression, and overall survival.

A total of 73 consecutive patients with mCRPC undergoing treatment with AA between November 2012 and October 2014 were included. Median follow-up was 9.9 (0.9-23.4) months. PSA decline>50% was found in 39% of the patients. Time to biochemical and radiological progression was 3.5 and 4.9 months, respectively. Overall survival was 13.2 months (95% CI: 9.0-17.4).

Our initial experience with AA in the routine management of patients with mCRPC demonstrates an efficacy-effectiveness gap compared with clinical trial. Except for PSA response (>50% decline) in patients managed with AA, postchemotherapy results were inferior to phase III studies. This is most likely because of patient selection, which is a typical weakness when transferring results from phase III trials into clinical practice.