Real-world use of enzalutamide in men with nonmetastatic castration-resistant prostate cancer in Japan

Background The purpose of the study is to evaluate real-world effectiveness and safety of enzalutamide in men with nonmetastatic castration-resistant prostate cancer (nmCRPC) in Japan. Methods This was a retrospective evaluation of medical records from men in Japan who started enzalutamide treatment from November 1, 2014, to March 31, 2018, and received androgen deprivation therapy throughout. The primary endpoint was time to prostate-specific antigen (PSA) progression. Secondary endpoints included PSA response rate, time to first use of new antineoplastic therapy, time to first use of cytotoxic chemotherapy, and enzalutamide treatment duration. An exploratory analysis of metastasis-free survival (MFS) was also performed. Adverse events (AEs) were analyzed to assess safety. Results Based on data from medical records of 205 men in Japan, median time to PSA progression was 27 months (95% confidence interval [CI] 19-not reached [NR]), with 82.5% and 52.0% of men achieving PSA response rates of >= 50% and >= 90%, respectively. Median time to first use of new antineoplastic therapy was 36 months (95% CI 27-NR) and median enzalutamide treatment duration was 13 months (interquartile range: 7-24). Median time to first use of cytotoxic chemotherapy was NR (95% CI 41-NR). Median MFS was 29 months (95% CI 23-35). In total, 51.7% of men experienced AEs, with malaise (18.5%), decreased appetite (10.7%), and nausea (4.9%) the most frequently reported. Conclusions This is the first study to demonstrate the real-world effectiveness and safety of enzalutamide in men with nmCRPC in Japan, further informing healthcare providers about available treatment options for this patient population.