Adherence Patterns for Abiraterone Acetate and Concomitant Prednisone Use in Patients with Prostate Cancer

BACKGROUND: With the growing use of oral anticancer medications, understanding adherence patterns has become increasingly important. Abiraterone acetate (AA) is a prodrug of abiraterone, a novel androgen biosynthesis inhibitor. AA is approved for use in combination with prednisone for treatment of patients with metastatic castration-resistant prostate cancer. OBJECTIVES: To evaluate AA and concomitant prednisone utilization and adherence patterns for patients with prostate cancer in the United States. METHODS: This study used data from 2 administrative health care claims databases—Dataset 1: Truven Health Analytics MarketScan (December 2010 to August 2012) and Dataset 2: Symphony Health Solutions’ ProMetis Lx (June 2009 to March 2013). To evaluate the consistency of medication-taking behavior, adherence was measured using medication possession ratio (MPR), which was calculated as the sum of days of supply divided by the days on therapy in patients with at least 2 AA prescriptions. Additional outcomes included the proportion of patients taking prednisone, mean and median daily dose of AA, and concomitant prednisone use. Adherence was also studied by age, health care plan type, or previous recent chemotherapy subgroups. RESULTS: 515 patients (mean age: 72.2) and 3,228 patients (mean age: 72.2) with at least 1 AA claim were selected from Dataset 1 and Dataset 2, respectively. The mean (median) daily AA dose per person per prescription was 998.8 (1,000) mg for Dataset 1 and 994.2 (1,000) mg for Dataset 2, which is within 1% of the recommended daily dose (1,000 mg). Mean (median) MPR was 93% (98%; n = 492) in Study Population 1 and 93% (100%; n = 2,449) in Study Population 2. The mean (median) daily prednisone dose per person per prescription was similar in both datasets with 10.1 (10.0; n = 488) mg and 10.6 (10.0; n = 2,425) mg in Dataset 1 and 2, respectively. Similar adherence patterns were observed for patients in different age groups, for patients with commercial health care plans versus patients with Medicare coverage, and for patients with recent chemotherapy compared with patients without. CONCLUSIONS: Results from 2 observational studies reported high levels of adherence to AA dosing and administration patterns consistent with prescribing information. These findings provide useful insights into the treatment patterns in patients with prostate cancer treated with AA and can contribute to the current discussion in oncologic research and practice.