Treatment duration and utilization patterns in metastatic castration-resistant prostate cancer patients receiving enzalutamide or abiraterone acetate.

Abstract

229 Background: Enzalutamide (ENZA) and abiraterone acetate (ABI) are approved hormonal therapies for men with metastatic castration-resistant prostate cancer (mCRPC). This study assessed real-world treatment duration and utilization patterns in patients receiving ENZA or ABI. Methods: Adult mCRPC patients initiating ENZA or ABI before or after cytotoxic chemotherapy were identified from the Truven MarketScan® claims database (2012–2015). The index date was the first initiation of ENZA or ABI; continuous insurance enrollment for ≥6 months prior to and ≥3 months after the index date was required. Treatment discontinuation was defined as a prescription gap of ≥45 days. Median treatment duration was estimated using Kaplan–Meier method. Treatment switching was defined as starting a new mCRPC-related therapy within 30 days before to 45 days after the discontinuation date. Analyses were separately conducted for chemo-naïve and chemo-experienced patients. Results: The study included 3230 chemo-naive (ENZA 920; ABI 2310) and 692 chemo-experienced patients (ENZA 262; ABI 430). Among chemo-naive patients, ENZA cohort was older (mean age 74.5 vs 73.5; p = 0.013), with a higher proportion of comorbidities vs ABI cohort. Treatment duration was longer for ENZA cohort than ABI cohort (log-rank p = 0.008; median = ENZA 10.7 vs ABI 8.8 months). Within 1 year of initiation, 55.7% of ENZA and 60.8% of ABI cohort discontinued treatment and 22.5% and 34.7%, respectively, switched to other mCRPC therapies. Results were consistent among subgroups with specific comorbidities. Treatment duration was shorter among chemo-experienced patients than chemo-naïve; the difference between ENZA vs ABI among chemo-experienced patients was not statistically significant (log-rank p = 0.255; median = ENZA 7.5 vs ABI 7.1 months). Conclusions: Despite a more complex profile at baseline, chemo-naive mCRPC patients in the ENZA cohort had a longer treatment duration and lower proportion of switching to other prostate-cancer-directed therapies vs the ABI cohort. The difference of treatment duration between the two cohorts was not statistically significant for chemo-experienced patients.