Abstract
Purpose We recently released the multi-institutional real-world analysis about the difference in survival outcomes between abiraterone acetate and enzalutamide against chemo-naïve castration-resistant prostate cancer (CRPC) in a first-line setting. Although reduced dose induction cases were included in that analysis, induction dose reduction might correlate with reduced efficacy. In this study, we analyzed full-dose induction subgroups from our overall cohort and investigated the true difference in efficacy between these agents. Methods A total of 220 chemotherapy-naïve CRPC cases treated with full-dose induction of first-line androgen receptor signaling inhibitor (ARSI) were analyzed. Outcome measures were prostate-specific antigen (PSA) response, PSA progression-free survival (PSA-PFS), treatment failure-free survival (TFF), cancer-specific survival (CSS), and overall survival (OS). Results Abiraterone acetate and enzalutamide were administered to 58 and 162 patients, respectively. The median PSA response rate (-65.4% (A) and -81.5% (E), p = 0.0252), PSA decline ≥ 90% (22.4% (A) and 37.0% (E), p = 0.0478), PSA-PFS (median four months (A) and seven months (E), p = 0.00833), TFF (median six months (A) and 15 months (E), p<0.0001), CSS (median 45 months (A) and not reached (E), p < 0.0001), and OS (median 34 months (A) and 80 months (E), p<0.001) were significantly better in the E group. Conclusion This study showed that PSA response, PSA-PFS, TTF, CSS, and OS were better with first-line enzalutamide administration. Direct inhibition of androgen receptor signaling by enzalutamide is associated with better clinical outcomes in the full-dose induction cohort.