A multicentre analysis of abiraterone acetate in Canadian patients with metastatic castration-resistant prostate cancer.

Abstract

The COU-AA-301 trial showed that abiraterone acetate (abiraterone), an oral cytochrome p450 CYP17 inhibitor, improved survival for men with metastatic castration-resistant prostate cancer (mCRPC) progressing after docetaxel. To better understand the non-clinical trial experience with abiraterone, we undertook a multicentre retrospective analysis of Canadian mCRPC patients treated with abiraterone. Consecutive patients with mCRPC who received abiraterone post-docetaxel were identified using centralized pharmacy records. These patients came from 5 Canadian tertiary cancer centres. Patients who received abiraterone for approved indications were included. Demographics, prognostic factors, treatment outcomes and adverse events were abstracted. We included 187 patients who initiated abiraterone between January 2011 and June 2012. The median age at diagnosis and abiraterone start was 65 and 73 years, respectively. Seventy-three (39%) patients had metastatic disease at diagnosis. The Eastern Cooperative Oncology Group (ECOG) performance status of 0, 1, 2 and 3 was noted in 17, 96, 39 and 8 patients, respectively. The median prostate-specific antigen (PSA) at abiraterone start was 132, with a median PSA doubling time of 2.8 months. The median follow-up of patients still on active follow-up was 13 months. The proportion of patients achieving a ≥50% PSA reduction was 64/177 (36%). PSA progression-free survival was 3.5 months (95% confidence interval [CI], 3.0, 4.0). Median overall survival from start of abiraterone was 11 months (95% CI, 8.0, 13) and 38 months (95% CI, 31, 41) from date of mCRPC. Anemia and fatigue were the most commonly reported adverse events. This study carries the inherent limitations of a retrospective chart review. The outcomes in this series of men treated with abiraterone in a non-trial setting were expected, considering previous clinical trials. Our results, therefore, support the generalizability of the COU-AA-301 study results.