Comparison of Out-of-pocket Costs and Adherence Between the Two Arms of the Prospective, Randomized Abiraterone Food Effect Trial

Purpose: Abiraterone acetate, prescribed for metastatic prostate cancer, has enhanced absorption with food. This effect was exploited in a randomized trial which showed noninferiority of PSA decline for 250 mg abiraterone with a low-fat meal (LOW) compared to 1,000 mg abiraterone fasting (STD). Drug was obtained via patient insurance. Patient out-of-pocket costs and adherence were surveyed.

Methods: Trial participants were randomized to STD or LOW, and surveys of adherence and out-of-pocket costs were administered at baseline and just before coming off study (follow-up).

Results: Out-of-pocket costs were available from 20 of 36 STD and 21 of 36 LOW patients. Median out-of-pocket costs for a month of drug were $0 (LOW) and $5 (STD); mean costs were $43.61 (LOW) and $393.83 (STD). The two groups did not differ significantly (p = 0.421). Maximum out-of-pocket cost was $1,000 (LOW) and $4,000 (STD). Monthly out-of-pocket costs > $500 were found in 1 LOW and 5 STD patients. For adherence, only 11 STD and 19 LOW patients had questionnaires completed at both baseline and follow-up. STD adherence was 98.18% at baseline and 91.69% at follow-up, differing significantly (p = 0.0078). LOW adherence was 96.52% at baseline and 97.86% at follow-up, not differing significantly (p = 0.3511). Adherence did not correlate with demographics. At follow-up, increasing adherence correlated significantly with decreasing dose (p = 0.013; rho =  - 0.458).

Conclusions: Out-of-pocket costs did not differ significantly in this limited analysis. Adherence was significantly different in STD as the trial progressed, which was not found in LOW.

Trial Registration: ClinicalTrials.gov NCT01543776; registered March 5, 2012.