Efficacy of abiraterone acetate for high-risk hormone-naive metastatic prostate cancer: A comparison with combined androgen blockade therapy with bicalutamide and androgen deprivation therapy alone

Background The treatment landscape for men with metastatic hormone-naive prostate cancer (mHNPC) has dramatically changed with the approval of next-generation anti-androgen drugs. We compared the treatment efficacy of abiraterone with that of combined androgen blockade (CAB) therapy and androgen deprivation therapy (ADT) alone in men with high-risk mHNPC. Methods In total, 146 Japanese men with high-risk mHNPC were retrospectively analyzed. As initial hormonal therapy, 30, 83, and 33 men were treated with ADT plus abiraterone (ABI group), ADT plus bicalutamide (CAB group), and ADT alone (ADT group), respectively. Treatment efficacy was compared using time to castration resistance (TTCR) and prostate-specific antigen (PSA) response among the groups. Propensity score matching analysis was also performed to adjust for baseline differences. Results The median (95% confidence interval [CI]) TTCR in the ABI, CAB, and ADT groups were not reached, 10.7 (7.6-13.8) months and 11.0 (7.9-12.4) months, respectively, and it was significantly longer in the ABI group than in the other groups (p = 0.0012, p = 0.0008). In propensity score matching analysis, the median TTCR was also significantly longer in the ABI group than in the other groups (hazard ratio [HR], 0.47; 95% CI, 0.22-0.98; p = 0.010; HR, 0.32; 95% CI, 0.12-0.85; p = 0.004). The number of men who achieved PSA levels <= 0.2 ng/mL after propensity score matching were significantly higher in the ABI group than in the other groups. Conclusions Our results provide important evidence regarding the superiority of abiraterone over CAB therapy and ADT alone for initial treatment for men with newly diagnosed mHNPC.