Purpose: Prostate cancer is the most commonly diagnosed cancer in the VA health care system, accounting for 31.8% of all incident cancer cases diagnosed in the VA. Nonadherence of oral anticancer medications is a costly problem with potentially harmful health effects. The extent of nonadherence among VA patients with prostate cancer is unknown. The purpose of our planned study is to evaluate (1) the number and percentage of prostate cancer patients receiving specific oral drug regimens (eg, abiraterone/prednisone and enzalutamide) for castrate-resistant prostate cancer; and (2) rates and patterns of medication nonadherence with these oral anticancer drugs.
Methods: This is the first-ever collaborative project by the Health Services Research AVAHO subcommittee. Each of the committee member’s VA medical centers (n = 8) will identify patients with metastatic prostate cancer receiving abiraterone/prednisone and enzalutamide via local systems, including IntelliDose e-prescribing systems and pharmacy applications coordinators. This patient list will be supplemented with data from VistA and local cancer registries, including patient age, comorbid conditions, stage of disease, prior therapies, prescription information, refill frequency, and medication possession ratio. We will conduct manual chart abstraction to determine whether patients transferred into or out of the VA system and reasons for nonadherence or discontinuation of oral medication therapy, including adverse effects or treatment failure. De-identified data will be transmitted to a central location for analysis. Planned statistical methods include logistic regression to determine patient, disease, and prior treatment characteristics associated with medication nonadherence.
Results: After IRB approval, data will be obtained from 8 participating sites. From the years 2011 to 2013, we will determine the total of number patients prescribed abiratarone and prednisone. Of these patients, we will report the percentage of patients that were nonadherent at some point during their treatment. We will also report the total number of patients prescribed enzalutamide and the percentage that were nonadherent at some point during their treatment.
Conclusions: This protocol has been developed collaboratively among multiple VAMC oncology programs. By evaluating the extent and reasons for medication nonadherence in this large veteran population, this study will provide useful information to guide clinical and pharmacy resource allocation for patient education and monitoring for our veterans on oral anticancer therapy. The Health Services Research AVAHO subcommittee welcomes collaborators from nonrepresented VA institutions, with particular interest in statistical support.