Trends in utilization of novel oral therapeutic agents for men with metastatic castrate-resistant prostate cancer within the United States Veteran’s Affairs Health System.

Abstract

220 Background: Therapeutic options for men with metastatic castrate resistant prostate cancer (mCRPC) have expanded significantly over the past 5 years with several new agents demonstrating improved survival, including two oral agents. Abiraterone acetate (AA), a CYP-17 androgen synthesis inhibitor, obtained initial FDA approval in 2011 for post-docetaxel (D) use, and gained expanded approval in 2012 for pre-D use. Enzalutamide (ENZ), an androgen receptor signaling inhibitor, also gained FDA approval in 2012 (post-D) and indication was expanded in 2014 (pre-D). Due to the relatively recent approvals of these agents, there is limited data on rates of uptake and prescribing patterns for patients (pts) with mCRPC. Methods: For this observational study, Veterans Affairs (VA) healthcare system data (including hospitalizations, outpatient visits, and pharmacy) were used to identify male veterans who received treatment for mCRPC between fiscal years 2008 and 2014. Descriptive statistics were used to classify treatment patterns. Results: During the time period, 75,199 pts with prostate cancer were medically or surgically castrated. Of those, 43,805 were treated with anti-androgens and 7,890 went on to receive advanced lines of therapy associated with mCRPC. The median age at the time of mCRPC treatment was 73y. Between 2008-2010 (pre-AA) and 2011-2014 (post-AA), the proportion of mCRPC pts treated with ketoconazole or D dropped from 95% to 59% (p < 0.0001). Conversely, the proportion of pts who received AA or ENZ increased from 19% to 68% (p < 0.0001). Among the 3,763 pts treated with AA or ENZ between 2011 and 2014, the proportion treated with first-line D decreased, while the proportion treated with first-line AA increased (p < 0.00001). Conclusions: The FDA approval of AA and ENZ has had a significant impact on treatment patterns for men with mCRPC within VA, with decreased use of ketoconazole and delayed use of chemotherapy. Further information regarding patient and disease characteristics is needed. The rapid uptake of these novel agents has significant implications for disease-related outcomes as well as anticipated pharmacy costs within the VA.