Survival with enzalutamide, an androgen inhibitor, was superior to bicalutamide in the treatment of men with castration-resistant prostate cancer (CRPC).1 Bicalutamide is currently the most common antiandrogen agent used in the second-line treatment of metastatic CRPC.

A total of 396 patients with nonmetastatic (M0) and metastatic (M1) CRPC were randomly assigned to receive 160 mg daily enzalutamide (198 patients) or 50 mg daily bicalutamide (198 patients) in the STRIVE (Safety and Efficacy Study of Enzalutamide Versus Bicalutamide in Men With Prostate Cancer) trial. Patients in both arms continued androgen deprivation therapy. The study’s primary endpoint was progression-free survival.

Treatment with enzalutamide resulted in a risk of disease progression or death that was 76% lower than those treated with bicalutamide for M0 and M1 patients (HR, 0.24; 95% CI, 0.18 – 0.32; P < .001), and 56% lower in M1 patients alone.

Patients treated with enzalutamide had a median progression-free survival of 19.4 months, compared to 5.7 months with bicalutamide.

STRIVE was the first trial to show a prolongation in progression-free survival between metastatic and nonmetastatic subgroups and was the first to show benefit with enzalutamide in those with nonmetastatic CRPC.

Enzalutamide was superior to bicalutamide in the study’s secondary endpoints. It was linked to an 81% reduction in the risk of prostate-specific antigen (PSA) progression (HR, 0.19; 95% CI, 0.14 – 0.26; P < .001) and proportion of patients with a ≥ 50% PSA response (81% vs 31%; P < .001).

RELATED: Experts Propose New Simplified Prostate Cancer Grading System

“It was the degree of effect that I found so striking,” said David Penson, MD, MPH, of the Department of Urologic Surgery, Vanderbilt University in Nashville, TN, in an interview with Cancer Therapy Advisor.

“I think that one of the reasons [we saw] such a marked difference is that the STRIVE population includes M0 patients. In general, I think these patients are being treated earlier in the course of their CRPC disease.”