Contemporary trends in abiraterone and enzalutamide prescription by provider specialty.

Abstract

366 Background: Androgen deprivation therapy (ADT) with LHRH-agonists and anti-androgens, is established in the management of prostate cancer and is administered by urologists, medical oncologists, and radiation oncologists. Newer agents for ADT, abiraterone acetate (ABI) and enzalutamide (ENZA) were approved by the FDA in 2011 and 2012, respectively, for the management of metastatic castrate resistant prostate cancer (mCRPC) after failing chemotherapy. We evaluated the contemporary economic burden of ABI and ENZA and their adoption by specialty. Methods: Because a majority of men with mCRPC are > 65 years of age, we utilized Medicare Part D data from 2013-15. The specific outcome variables of interest included the aggregate reimbursement and total number of prescriptions for ABI and ENZA, by specialty. Descriptive statistics and trend analysis were performed. Results: From 2013-15, the total number of prescription rose from 52457 to 81058 for ABI and from 17141 to 69181 for ENZA. Though medical oncologists prescribed more than 75% of ABI/ENZA prescriptions each year, the proportion of prescriptions written by urologists increased annually. The greatest increase in the percentage of prescriptions originating from urology occurred from 2013-2014 for ABI (3.96% to 8.62%) and from 2014-15 for ENZA (5.42% to 15.64%); meanwhile, prescriptions by radiation oncology were negligible throughout the study. Southern states accounted for greater than one third of ABI and ENZA prescriptions. By 2015, the aggregate reimbursement of Part D claims for ENZA and ABI was $790 million each. Among all medication claims, ENZA and ABI represent the 29th and 30th most expensive by aggregate cost. Conclusions: While medical oncologists account for the vast majority of ENZA and ABI prescriptions, the prescriptions by urologists is increasing while prescriptions by radiation oncologists remain negligible. Though approved for mCRPC patients, ENZA and ABI are already among the costliest medications covered by Medicare. As Level 1 indications for the use of these medications increase and now include castrate-sensitive patients, further study should be directed at determining optimal timing and indication for prescription.