To analyze the drug adherence rates and overall survival for in patients treated with arbiraterone acetate (AA) for castration-resistant prostate cancer (CRPC).
The database of the largest insurance company in Austria (Wiener Gebietskrankenkasse) was analyzed. Data on all CRPC patients with at least one prescription of AA between November 2011 and December 2014 in the postchemotherapy setting were collated and compared to the Austrian death and hospital admission statistics. Drug adherence was estimated by the medication possession ratio (MPR).
Data of 270 patients (mean age 73.5 ± 8.9 years) were analyzed. The mean duration of AA treatment was 9.8 months (range 1–38 months). The duration of AA treatment was as follows: 0–2 months 53 patients (19.6 %), 3–5 months 73 patients (28.1 %), 6–10 months 67 patients (24.8 %) and >10 months 97 patients (35.9 %). The median MPR was 100 % and in 241 (89.2 %) the MPR exceeded ≥80 %. The median overall survival (OS) was 11 months. Based on Kaplan-Meier analysis, the 6 month OS was 61 %, 12 month OS 43 %, 18 month OS 35 % and >24 month OS 24 %. The OS was strongly correlated to patient age and the duration of AA treatment. Of all 270 patients, only 19 (7 %) were not hospitalized during their remaining life span and 71 (26.2 %) spent more than 50% of their remaining life span in hospital care.
The OS was shorter than in phase III trials and strongly correlated to patient age and the duration of AA treatment. The high mortality rate within the first 6 months of AA treatment in this real-life setting suggests a less stringent patient selection than in a phase III trial.