Abstract
e16542 Background: As the use of oral therapies in mCRPC increases, it is crucial to understand treatment persistence as it may be used as an effectiveness outcome. This study evaluated treatment persistence in chemotherapy-naïve and post-chemotherapy patients with mCRPC treated with ENZA and AA+P in the United States. Methods: A retrospective claims database analysis identified mCRPC patients treated with ENZA or AA+P from January 1, 2010, to November 30, 2015 . The Clinformatics Data Mart database (OptumInsight, Eden Prairie, MN) included Medicare and commercially insured patients. Treatment persistence (time from first dose to discontinuation [gap > 30 days without index drug]) was assessed in subpopulations of chemotherapy-naïve and post-chemotherapy patients using Kaplan Meier plots with log-rank test. Hazard ratios (HR) [ENZA only/AA+P only] with 95% confidence intervals (CIs) were calculated using a Cox proportional hazards model. Results: In total, 2792 patients with mCRPC received ENZA (n = 827) or AA+P (n = 1965) after September 1, 2012, including subsets of ENZA-only (n = 689) and AA+P-only (n = 1329) patients. Mean age was 74 years and 75% were enrolled in a Medicare plan; 1689 patients with mCRPC were chemotherapy-naïve and 329 were post-chemotherapy. Overall, baseline characteristics were similar between the cohorts except for a higher comorbidity burden in the ENZA-only cohort. Median persistence in chemotherapy-naïve patients was longer with ENZA (ENZA only: 240 days [95% CI 197, 272] versus AA+P only: 186 days [95% CI 180, 212]) (HR 0.86; p = 0.02). In the post-chemotherapy cohort, median persistence was similar (ENZA only: 131 days [95% CI 107, 180] versus AA+P only: 127 days [95% CI 97, 172]) (HR 1.06; p = 0.64). Conclusions: In this real-world mCRPC analysis, treatment persistence was significantly longer in chemotherapy-naïve patients treated with ENZA only versus AA+P only; in post-chemotherapy patients, persistence was not statistically different. Treatment persistence may be utilized an as indicator of treatment effectiveness in clinical practice.
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