Enzalutamide (ENZ) and abiraterone plus prednisolone (ABI) can improve the survival of patients with castration-resistant prostate cancer (CRPC). However, the agent that is more effective against nonmetastatic CRPC remains unclear. To evaluate the agent that can be used as the first-line treatment for CRPC, an investigator-initiated, multicenter, randomized controlled trial (ENABLE Study for PCa) including both metastatic and nonmetastatic CRPC was conducted in Japan. The prostate-specific antigen (PSA) response rate, overall survival, some essential survival endpoints, and safety of patients with nonmetastatic CRPC were also analyzed. In this subanalysis, 15 and 26 patients in the ENZ and ABI arms, respectively, presented with nonmetastatic CRPC. There was no significant difference in terms of the PSA response rate between the ENZ and ABI arms (80% and 64%, respectively; p = 0.3048). The overall survival did not significantly differ between the two arms (HR: 0.68; 95% CI: 0.22-2.14, p = 0.5260). No significant differences were observed in terms of radiographic progression-free survival and cancer-specific survival between the ENZ and ABI arms (HR: 0.81; 95% CI: 0.35-1.84; p = 0.6056 and HR: 0.72; 95% CI: 0.19-2.73; p = 0.6443, respectively). Only four and six patients in the ENZ and ABI arms, respectively, had ≥grade 3 adverse events. ABI and ENZ had similar efficacy and safety profiles in patients with nonmetastatic CRPC.
Keywords: abiraterone; castration-resistant; enzalutamide; nonmetastatic.