Abiraterone Acetate in Asymptomatic or Mildly Symptomatic Patients With Metastatic Castration-Resistant Prostate Cancer

This is a randomized (individuals will be assigned by chance to study treatments),

double-blind (individuals and study personnel will not know the identity of study

treatments), placebo (an inactive substance that is compared with a drug to test whether

the drug has a real effect in a clinical trial)-controlled study in approximately 1,000

medically or surgically castrated male patients with metastatic CRPC who have shown tumor

progression and are asymptomatic or mildly symptomatic. The study period will consist of

screening, treatment, and follow-up phases. Patients will receive study treatment

(abiraterone acetate or placebo) plus prednisone until radiographic progression of

disease and/or unequivocal clinical progression. Efficacy evaluations will be performed

throughout the treatment period and safety will be assessed until 30 days after the last

dose of abiraterone acetate. throughout the study. Follow-up will continue for up to 60

months (5 years) or until the patient dies, is lost to follow-up, or withdraws informed

consent. At the interim analysis of overall survival (OS; 43% of death events), the

independent data monitoring committee (IDMC) reviewed the efficacy and safety data and

concluded that all of the data pointed to a significant advantage for patients in one arm

of the study compared with the other arm thereby unanimously recommending unblinding the

study and allowing crossover from the placebo arm to active therapy. Patients currently

receiving placebo will be offered crossover therapy to abiraterone acetate. Treatment for

patients who were originally randomized to the abiraterone acetate treatment group will

not change. Patients will be discontinued from long term follow-up at the time of the

Clinical Cut-Off Date for Final Analysis (CCO-FA); however, patients still receiving

treatment with abiraterone acetate at the CCO-FA will be offered to receive continued

treatment for an additional period of up to 3 years or until disease progression or

unacceptable toxicity. For these patients, safety assessment will be performed while

continuing treatment, and for 30 days after the last dose of abiraterone acetate.