Methods: Adult chemotherapy-naïve patients with confirmed prostate adenocarcinoma, Eastern Cooperative Oncology Group (ECOG) performance status (PS) grade 0-1, ongoing androgen deprivation (serum testosterone <50 ng/dL) with prostate specific antigen (PSA) or radiographic progression were randomized to receive abiraterone acetate (1000 mg, QD) + prednisone (5 mg, BID) or placebo + prednisone (5 mg, BID), until disease progression, unacceptable toxicity or consent withdrawal. Primary endpoint was improvements in time to PSA progression (TTPP).

Results: Totally, 313 patients were randomized (abiraterone: n = 157; prednisone: n = 156); and baseline characteristics were balanced. At clinical cut-off (median follow-up time: 3.9 months), 80% patients received treatment (abiraterone: n = 138, prednisone: n = 112). Median time to PSA progression was not reached with abiraterone versus 3.8 months for prednisone, attaining 58% reduction in PSA progression risk (HR = 0.418; p p p = 0.0369). Median survival was not reached. Most common (≥10% abiraterone vs. prednisone-treated) adverse events: bone pain (7% vs. 14%), pain in extremity (6% vs. 12%), arthralgia (10% vs. 8%), back pain (7% vs. 11%), and hypertension (15% vs. 14%).