(ChemotherapyAdvisor) – Abiraterone acetate (AA) plus prednisone (P) produced a statistically significant improvement in radiographic progression-free survival (rPFS) and a strong trend for increased overall survival (OS), according to the results of a study presented by a multinational team of researchers at the 2012 American Society of Clinical Oncology Annual Meeting. The abstract presented was entitled “Interim analysis (IA) results of COU-AA-302, a randomized, phase III study of abiraterone acetate (AA) in chemotherapy-naive patients (pts) with metastatic castration-resistant prostate cancer (mCRPC).”

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Previous studies have shown that AA, an androgen biosynthesis inhibitor, improves OS patients with metastatic castrate-resistant prostate cancer (mCRPC) that had previously progressed on docetaxel. The investigators of this current study (known as COU-AA-302) aimed to compare the clinical benefit of AA plus P vs placebo (PL) + P in chemo-naive, asymptomatic/mildly symptomatic mCRPC patients. Co-primary end points for the study were rPFS and OS.

The Independent Data Monitoring Committee concluded that the OS, rPFS and secondary end points all favored the AA arm and unanimously recommended un-blinding the study and crossing patiens from PL to AA at interim analysis (43% of total events). Median follow-up was 22.2 months. At the time of IA, the median rPFS and median OS had not been reported for the abiraterone arm and were 8.3 and 27.3 months, respectively, in the placebo arm. Grade 3/4 adverse events for the abiraterone arm vs placebo arm were hypertension 3.9% vs 3.0%; hypokalemia 2.4% vs 1.9%; elevated ALT 5.4 vs 0.7; elevated AST 3.0 vs 0.9.

The investigators concluded that “AA plus P produced a statistically significant improvement in rPFS and a strong trend for increased OS at this IA, and that, while median OS (AA arm) has not been reached, median PL arm OS (27.2 months) is the longest measured in any phase 3 mCRPC study.”