There are several new therapies available to treat men with advanced prostate cancer; however, the decision making tools needed to determine the best treatment for these patients are noticeably absent. The prostate-specific membrane antigen (PSMA) is increasingly being recognized as an important target for prostate cancer imaging and determining the most effective therapy. Accordingly, a wide variety of agents are being used to image PSMA. One of these agents is 18F-DCFPyL. In this study the investigators will image men with advanced prostate cancer using 18F-DCFPyL and a positron emission computed tomography (PET/CT) scanner. The investigators will compare the results of 18F-DCFPyL PET/CT for the detection of metastases and monitoring the effects of therapy with conventional imaging (CT, bone scan) and clinical follow-up. In this way, the investigators will evaluate the benefit of using 18F-DCFPyL PET/CT to decide what is the best treatment strategy for a man with advanced prostate cancer.