A Biomarker Study of Standard-of-care Radium-223 Chloride for Metastatic Castration-resistant Prostate Cancer

This research study is a Phase II clinical trial. Phase II clinical trials test the safety and effectiveness of an investigational intervention to learn whether the intervention works in treating a specific disease. "Investigational" means that the intervention is being studied. This research study is designed to examine a treatment strategy that is standard but still relatively new. Ra-223 consists of a series of six infusions given once every 4 weeks. It was FDA approved in 2013 for the treatment of prostate cancer that has spread to bone and has grown despite ADT ("hormonal therapy"). Ra-223 was approved because it was shown to improve the length of the lives of the men with prostate cancer who received it. Despite that important benefit, it is not known to improve other standard markers of prostate cancer such as PSA blood tests (a blood marker that is used to track cancer activity in men who have prostate cancer) and standard imaging scans such as bone scans and computed tomography (CT) scans. If participants and their doctors do not have good markers of whether or not the cancer is responding to therapy, it is harder to make decisions about whether to continue that therapy. This is a current problem. This study makes use of Ra-223 in the standard FDA-approved way, but adds non-standard testing in an attempt to gain insight about how the drug works and how best to track patients who are receiving the drug.