Enzalutamide after Abiraterone Acetate Therapy in Docetaxel-Experienced or -Naïve Patients with Metastatic Prostate Cancer
Although the activity of enzalutamide after therapy with abiraterone acetate and docetaxel has been well documented before (Nadal R, et al. Prostate. 2014;Aug 31 [Epub ahead of print]), there are limited data on the efficacy of enzalutamide after abiraterone therapy in chemotherapy-naïve patients with metastatic castrate-resistant prostate cancer (mCRPC). Azad and colleagues examined the British Columbia Cancer Registry for patients with mCRPC who had received enzalutamide after abiraterone, and who had previously received chemotherapy with docetaxel or not (Azad AA, et al. ESMO 2014: Abstract 788P).
As shown in the Table, no significant differences were shown in prostate-specific antigen (PSA) reduction, median time to progression (TTP), or median overall survival (OS) in patients treated with enzalutamide after abiraterone therapy, regardless of whether they had previously been treated with docetaxel. The researchers conclude that the antitumor activity of enzalutamide after abiraterone was comparable in docetaxel-experienced or in docetaxel-naïve patients, suggesting that docetaxel is not linked to cross-resistance between enzalutamide and abiraterone.
However, this study did not identify clinical or molecular factors predictive of which patients would respond to enzalutamide after abiraterone therapy, an outcome that remains a high priority for future research. Moreover, the lack of statistical significance among the docetaxel-experienced and docetaxel-naïve groups may be because of the small number of patients included in the study; it is possible that a higher-powered analysis might have led to different results.