Adherence to abiraterone among the first 86 recipients after release in Saskatchewan

Metastatic castration-resistant prostate cancer is now commonly treated with abiraterone, an orally administered chronic medication. Although abiraterone has certain advantages over docetaxel-based therapy, patients are now responsible for ensuring optimal adherence to their medication. To our knowledge, adherence to abiraterone in a real-world setting has never been described. The objective of the present study was to measure adherence to abiraterone among the first patients to receive the drug in Saskatchewan. Electronic pharmacy claims were obtained from the Saskatchewan Cancer Agency after removal of patient names and identifiers. All patients with at least 1 dispensation for abiraterone between August 2011 and October 2013 were eligible. The primary endpoint was the percentage of patients achieving optimal adherence at 6 months, defined as a medication possession ratio (mpr) of 80% or better. During the study period, 141 patients received abiraterone, among whom 86 could be followed for at least 6 months. Optimal adherence was achieved in 82.6% of patients (71 of 86) at 6 months, with 79.1% achieving a mpr of at least 90%. Of patients with available follow-up to 1 year, 81.6% (31 of 38) maintained optimal adherence during the entire period.