Efficacy and Safety Profile of Enzalutamide for Japanese Patients with Castration-resistant Prostate Cancer.

Enzalutamide is a novel, non-steroidal anti-androgen that was approved for the treatment of patients with castration-resistant prostate cancer (CRPC) in 2014 in Japan. To assess the potency of enzalutamide treatment in Japan, we performed a pilot retrospective study. Among 91 patients who received treatment in our Institution between May 2014 and July 2015, 51 patients with docetaxel-naïve CRPC (56.0%) underwent enzalutamide therapy. The median progression-free survival (PFS) and overall survival (OS) were 10.2 months and 27.9 months, respectively. The remaining 40 patients with CRPC (44.0%) underwent enzalutamide therapy after docetaxel. The median PFS and OS were 4.4 months and not reached, respectively. Among patients with docetaxel-naïve CRPC, 12 (24%) experienced adverse events, whereas 16 (40%) experienced adverse events after docetaxel. Fatigue (15%) and appetite loss (13%) were the most common. We partially clarified the characteristics of enzalutamide therapy in Japan. The PFS associated with enzalutamide might be shorter in Japanese patients.