A multicenter population-based experience with abiraterone acetate (AA) in patients with metastatic castration resistant prostate cancer (mCRPC).

113 Background: The COU-AA-301 trial showed that abiraterone (AA), an oral cytochrome p450 CYP17 inhibitor, improved survival for men with mCRPC progressing after docetaxel. AA is now a standard treatment in this setting. In order to better understand the non-clinical trial experience with AA, we undertook a multicenter retrospective analysis of patients (pts) treated with AA. Methods: Consecutive pts with mCRPC from 5 tertiary cancer centers in Canada who had received AA post-docetaxel were identified using centralized pharmacy records for each center. Pts who received AA for approved indications or within expanded access programs were included. Demographics, prognostic factors, treatment outcomes and toxicity profiles were collected. Results: One hundred and eighty seven pts, who initiated AA between Jan-2011 and Jun-2012, were included. Median age at diagnosis and AA start was 65 and 73 years. 73 (39%) pts had M1 disease at diagnosis. ECOG 0/1/2/3 was noted in 17/96/39/8 pts. Median PSA at AA start was 132 with a median PSAdt of 2.8 months. 54 (29%) pts received more than 1 prior course of chemotherapy. Median follow up was 20.5 months. Median survival from start of AA was 9.3 months (95% CI, 7.9-12.6). Regional results were: Alberta 14 months (95% CI, 13-18); BC 8.2 months (95% CI, 5.4-9.6); and Ontario 7.3 months (95% CI, 5.7-8.1). Median overall survival from date of mCRPC was 36 months (95% CI, 29-40); in Alberta this was 39 months (95% CI, 29-47); BC 26 months (95% CI, 18-41); and Ontario 33 months (95% CI, 25-41). AA was well tolerated with toxicities comparable to those seen in the trial population, with anemia and fatigue being the most common reported toxicity. Conclusions: This is one of the largest cohorts of men with mCRPC treated with AA in the non-clinical trial setting. Treatment outcomes corroborate with results reported in clinical trials, supporting the effectiveness of AA in an unselected population. A difference in survival outcomes between the different cancer regions can be attributed to differences in time to AA start. Future analyses to evaluate potential prognostic/predictive factors will be undertaken.