Abiraterone acetate significantly prolongs overall survival in men with metastatic castration-resistant prostate cancer (mCRPC) that has progressed after treatment with docetaxel, the final analysis of a large, multicenter study published in The Lancet Oncology has confirmed (2012;13:983-992).
Under the brand name Zytiga, abiraterone acetate received FDA approval in April 2011 for use in combination with prednisone for the treatment of mCRPC in men who had received prior docetaxel (Taxotere). The pill targets the cytochrome P450 17a1 (CYP17A1) protein, which plays an important role in testosterone production.
Abiraterone had already demonstrated improved overall survival (OS) in mCRPC in an interim analysis of a phase 3 study funded by Janssen Research & Development. (Zytiga is a product of Janssen Biotech, Inc.) The study enrolled 1,195 men at 147 sites in 13 countries. All patients had mCRPC that had progressed after docetaxel therapy.
The final study analysis focused on the 797 patients who had been randomly assigned to receive abiraterone plus prednisone and the 398 patients who had been given placebo plus prednisone. At median follow-up of 20.2 months:
- Median OS for the abiraterone group was 15.8 months, compared with 11.2 months for the placebo group.
- Median time to prostate-specific antigen (PSA) progression was 8.5 months for the abiraterone group vs 6.6 months for the placebo group.
- Median radiologic progression-free survival was 5.6 months for the abiraterone group and 3.6 months for the placebo group.
- A greater proportion of patients had a PSA response in the abiraterone group (235 of 797 patients, or 29.5%) than in the placebo group (22 of 398 patients, or 5.5%).
The most common grade 3-4 adverse events were fatigue, in 72 of 791 (9%) abiraterone users and 41 of 394 (10%) placebo users; anemia (62 [8%] vs 32 [8%], respectively); back pain (56 [7%] vs 40 [10%], respectively); and bone pain (51 [6%] vs 31 [8%], respectively).