Abiraterone acetate, enzalutamide and their sequence for castration-resistant prostate cancer

To analyze drug adherence, overall survival (OS) and hospitalization rates of patients with castration-resistant prostate cancer (CRPC) treated with arbiraterone acetate (AA), enzalutamide (ENZ) and their sequence in a real-life setting.

The database of the largest public insurance company in Austria was analyzed. All CRPC patients with at least one prescription of AA and/or ENZ between September 2013 and August 2016 in the pre-chemotherapy and post-chemotherapy setting were extracted and matched to the Austrian death and hospital admission statistics. Drug adherence was estimated by the medication possession ratio (MPR).

Data of 457 patients (mean age: 74.4 ± 8.5 years) were analyzed. The mean MPR was 90% for AA, 85% for ENZ and 88% for the sequence therapy cohort. The median overall survival (OS) of the entire cohort was 21 months: 15 months for AA, 24 months for ENZ, 26 months for the sequence group, and 10 months for the sequence group after switching. In the post-chemotherapy setting, the median OS was 14 months in AA treatment (mean: 15.8 ± 0.9 months), 19 months in the ENZ treatment (mean: 17.2 ± 1.4 months) and 25 months in the sequence group (mean: 22.7 ± 0.8 months). Median OS in the pre-chemotherapy setting was 25 months (mean: 21.5 ± 1.1 months), 18 months in AA treatment group (mean: 18.9 ± 1.5 months) and 17 months in ENZ treatment group (mean: 18.2 ± 1.9 months). Only 43 (9.4%) patients were not hospitalized during the course of the study. On average patients spent 13% of their remaining life span in hospital care (median 8%, range: 1–34%).

This Austrian prescription database allows some insights into the outcome of CRPC patients treated with AA and ENZ and their sequence in a real-life setting. Drug adherence was satisfactory, OS was shorter for AA and ENZ as compared to the pivotal phase III trials.