PROSPER: A phase 3, randomized, double-blind, placebo (PBO)-controlled study of enzalutamide (ENZA) in men with nonmetastatic castration-resistant prostate cancer (M0 CRPC).

3Background: Men with M0 CRPC and rapidly rising prostate-specific antigen (PSA) are at high risk of developing metastatic (M1) CRPC. ENZA improves overall survival (OS) and radiographic progression-free survival in men with M1 CRPC. We hypothesized that ENZA will improve metastasis-free survival (MFS) in men with M0 CRPC. Methods: Eligible men with M0 CRPC, PSA doubling time ≤ 10 mo and PSA ≥ 2 ng/mL at screening continued androgen deprivation therapy (ADT) and were randomized 2:1 to ENZA 160 mg or PBO. The primary endpoint was MFS. Secondary endpoints included time to PSA progression, time to first use of new antineoplastic therapy, OS and safety. Results: In 1401 men, ENZA significantly prolonged median MFS (36.6 mo vs 14.7 mo [P < .0001]), time to first use of new antineoplastic therapy (39.6 mo vs 17.7 mo [P < .0001]) and time to PSA progression (37.2 mo vs 3.9 mo [P < .0001]) compared to PBO (Table). In the first interim analysis of OS there was a trend in favor of ENZA (hazard ratio [HR] = 0.80; P ...