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 2 oral agents. Abiraterone acetate (AA), a CYP-17 androgen synthesis inhibitor, obtained initial FDA approval in 2011 for post-docetaxel (DXT) use and gained expanded approval in 2012 for pre-DXT use. Enzalutamide (ENZ), an androgen receptor signaling inhibitor, also gained FDA approval in 2012 (post-DXT) and indication was expanded in 2014 (pre-DXT).
Purpose: The objective is to provide insight into the uptake of novel therapeutics and its impact on treatment for patients 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. Sequencing patterns and treatment duration were assessed. Descriptive statistics were employed.
Results: During the study period, 8,774 patients initiated advanced lines of therapy associated with mCRPC. AA, DXT, and ketoconazole (KCZ) were the most commonly used firstlines of advanced therapies (24.6%, 24.8%, 47.0%, respectively). Between 2008 and 2013, the proportion of mCRPC patients treated with first-line DXT or KCZ dropped from 98% to 38% (P < .0001) while the proportion who received first-line AA increased to 58% (P < .0001). Furthermore, among the 4,169 patients treated with AA between 2011 and 2014, the proportion treated pre-DXT increased from 32% to 80% (P < .0001). AA was also the most common second-line treatment received. Between 2012 and 2013, ENZ use was low but increased dramatically. Among patients who initiated DXT, KCZ, or AA as first-line treatment in 2011/2012, median time on initial treatment was 5.9, 9.1, 11.5 months, respectively.
Conclusions: The FDA approval of AA and ENZ had a significant impact on treatment patterns for men with mCRPC within VA and was associated with decreased use of KCZ 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.
