Impact of abiraterone acetate with and without prior docetaxel chemotherapy on the survival of patients with metastatic castration-resistant prostate cancer: a population-based study.

BACKGROUND: Abiraterone acetate was introduced in Quebec in 2012 for the treatment of metastatic castration-resistant prostate cancer (mCRPC) in patients who had received chemotherapy with docetaxel. This study describes abiraterone use in the early postapproval period and its clinical effectiveness in Quebec, for both patients who had received docetaxel chemotherapy and those who could not receive docetaxel therapy owing to medical reasons.

METHODS: A retrospective cohort study was conducted using Quebec public health care administrative databases. Our cohort consisted of patients with mCRPC who received abiraterone between January 2012 and June 2013. Treatment groups were defined as patients who received abiraterone following docetaxel chemotherapy and those who received abiraterone without having had chemotherapy, under the "exception patient" measure. Study outcomes included overall survival, duration of abiraterone therapy and number of hospital days. Cox proportional hazard regression was used to estimate the effectiveness of abiraterone adjusted for several covariates.

RESULTS: Our cohort consisted of 303 patients with mCRPC treated with abiraterone (99 after chemotherapy and 204 as exception patients). The median age at initiation of abiraterone therapy was 75.0 for the postchemotherapy group and 80.0 for the exception patient group. The corresponding median survival values were 12 and 14 months (log-rank test p = 0.8). Risk of death was similar in the 2 groups (adjusted hazard ratio 0.89 [95% confidence interval 0.57-1.38]).

INTERPRETATION: The effectiveness of abiraterone in older patients who were ineligible for chemotherapy was similar to that of patients with prior docetaxel exposure. Overall, the real-world survival benefits of abiraterone were similar to those in the COU-AA-301 trial.