Study of Abiraterone Acetate in Participants With Metastatic Castration-Resistant Prostate Cancer (mCRPC), Chemo-Naive, Who Received a Prior Diethylstilbestrol Therapy

This is a Phase 2, multinational (when medical research study takes place in more than one country), multicenter (when more than one hospital or medical school team work on a medical research study), open-label (all people know the identity of the intervention), and single arm study to determine benefits of abiraterone acetate and low-dose prednisone to androgen deprivation therapy (ADT) in mCRPC participants who failed to prior DES therapy. The study will consist of a Screening Phase of up to 28 days before enrollment; a PSA Evaluation Phase; and a Follow-up Phase of up to 24 months. Each cycle of abiraterone therapy will be of 28 days. Participants will receive 1000 milligram (mg) abiraterone acetate orally once daily plus prednisone 5 mg orally once daily plus stable regimen of ADT (luteinizing hormone-releasing hormone \[LHRH\] agonists) as per Investigator's discretion. Treatment will continue until PSA progression, clinical progression, consent withdrawal, or the occurrence of unacceptable toxicity. Efficacy will primarily be assessed by time to PSA progression. Participants' safety will be monitored throughout the study.