Presentation Authors: Krishnan Ramaswamy, New York, NY, Stanislav Lechpammer, San Francisco, CA, Jack Mardekian, New York, NY, Neil M. Schultz, Northbrook, IL, Ahong Huang, Li Wang, Plano, TX, Onur Baser, Ann Arbor, MI, Daniel George*, Durham, NC
Introduction: Prostate cancer (PC) is the 2nd leading cause of cancer death among US males and accounts for a great proportion of health expenditures. The objective of this study was to evaluate overall survival (OS) and economic outcomes in chemotherapy-naive metastatic castrate resistant prostate cancer (mCRPC) patients treated with abiraterone acetate or enzalutamide.
Methods: A retrospective analysis was performed on 3,174 male patients (â‰¥18 years) using the Veterans Health Administration (VHA) database. mCRPC patients with evidence of surgical or medical castration, â‰¥1 pharmacy claim for abiraterone acetate or enzalutamide (1st claim date = index date) following surgical or medical castration and with no chemotherapy treatment during the 12 months pre-index date were identified from 01 April 2014 to 31 March 2017. Patients had continuous VHA enrollment for â‰¥12 months pre- and post-index date and were followed until death or disenrollment. Kaplan-Meier analysis was conducted to estimate OS and Cox proportional hazards regression models examined the impact of treatment on survival. Patients initiating abiraterone acetate were 1:1 propensity score matched (PSM) with those initiating enzalutamide. All-cause and PC-related resource use and costs per-patient-per-month (PPPM) were compared between the matched cohorts during the 12 months post-index date.
Results: This study included 1,945 abiraterone acetate and 1,229 enzalutamide mCRPC patients with mean ages of 73 and 74 years respectively. After a median follow-up of 18 months and 19 months, enzalutamide and abiraterone acetate patients had a median survival time of 30 months and 26 months, respectively. In the Cox analysis, enzalutamide patients had better survival compared to abiraterone acetate patients (HR=0.87; 95%CI 0.78-0.96). After PSM, there were 1,160 patients left in both cohorts. Compared to abiraterone acetate patients, enzalutamide patients had fewer mean all-cause outpatient visits PPPM (2.51 vs 2.86; p < .0001) and fewer mean PC-related outpatient visits PPPM (0.86 vs 1.03; p < .0001). Enzalutamide patients also had lower mean all-cause outpatient costs PPPM ($2,588 vs $3,115; p < .0001) and mean total costs PPPM ($8,085 vs $9,092; p=.0002); lower mean PC-related outpatient costs PPPM ($1,356 vs $1,775; p < .0001) and mean total costs PPPM ($6,321 vs $7,280; p < .0001) than abiraterone acetate patients.
Conclusions: Chemotherapy-naive mCRPC patients treated with enzalutamide had better survival, significantly lower resource use and healthcare costs than patients treated with abiraterone acetate.
Source of Funding: This study was funded by Pfizer Inc.