Purpose: The treatment of metastatic castration-resistant prostate cancer (mCRPC) has changed significantly with the addition of 2 oral hormonal agents: abiraterone and enzalutamide. The purpose of this review was to define the progression free survival (PFS) and overall survival (OS) of patients receiving abiraterone pre- and postdocetaxel, determine the clinical benefit of sequential use of enzalutamide, and examine the tolerability of these agents in the veteran population.
Methods: A retrospective review of patients with mCRPC who received abiraterone and enzalutamide at VA Pittsburgh Healthcare System was conducted between June 1, 2011, and December 1, 2014.
Results: Forty-seven patients were included. Docetaxel was utilized first line in 29 patients, 18 patients had abiraterone first line, and 17 patients received enzalutamide following abiraterone. The average age was 74 years, most patients were white (81.6%), with a median Gleason score of 8. Median PFS for all patients on abiraterone was 5.2 months, 4.9 months for patients on abiraterone following docetaxel, and 4.45 months for patients on abiraterone first line (P = .41). Median OS was 9.6 months for all patients who received abiraterone; there was no significant difference between patients on abiraterone pre- or postdocetaxel (P = .26). Abiraterone prostate-specific antigen (PSA) response rate (RR) was 93.7%, enzalutamide PSA RR (defined by any de-crease in PSA) was only 35.3%. The median duration of PSA response and median duration of radiographic response for enzalutamide were 2.1 months and 3.92 months, respectively.Both agents were tolerated with minimal toxicity.
Conclusions: This is the first efficacy data comparison of abiraterone pre- and postdocetaxel and sequential enzalutamide after abiraterone reported in a veteran population. The PFS and OS of abiraterone pre- and postdocetaxel were not different. The short duration of response may be due to the older age of veterans, high Gleason score, and small sample size. The PSA RR and radiographic RR of sequential use of enzalu-tamide after abiraterone in veteran patients with mCRPC were short. This was compatible with data reported in the literature. There may be a cross-resistance between the 2 hor-monal agents. The best sequence is unknown at this time. A trial of upfront enzalutamide followed by abiraterone or a combination of both agents is warranted.
