A clinicial research study for patients with asymptomatica/mildly symptomatic castration resistant prostate cancer and two or more bone metastases. Bayer HealthCare is seeking men to participate in a research study of radium-223. The purpose of the ERA 223 trial is to determine if the addition of radium-223 to abiraterone acetate is able to prolong life and to delay events specific for prostate cancer which has spread to the bone, such as bone fractures or bone pain which needs to be treated with an X-Ray machine. This study is enrolling pateints with prostate cancer who, despite medical or surgical castration, have rising prostate specific antigen (PSA) levels. Eligible patients must have two or more bone metastases with no visceral, e.g. liver metastases and not have received prior chemotherapy. Prostate cancer lesions must be asymptomatic or mildly symptomatic. All patients will receive abiraterone acetate along with either radium-223 or placebo.