A Positron Emission Tomography/Computed Tomography (PET/CT) Bone Imaging Study in Patients Receiving Enzalutamide for Castration-Resistant Prostate Cancer (CRPC)

Inclusion Criteria: * Histologically or cytologically confirmed adenocarcinoma of the prostate without neuroendocrine differentiation, or signet cell or small cell features; * Presence of bone metastatic disease as assessed by at least two lesions on whole body metastable technetium-methylene diphosphonate (99mTc-MDP) bone scintigraphy; * Throughout the study, ongoing androgen deprivation therapy with a luteinizing hormone-releasing hormone (LHRH) analogue or prior bilateral orchiectomy (medical or surgical castration); * Testosterone ≤ 1.73 nmol/L (≤ 50 ng/dL) at screening; * Progressive disease on androgen deprivation therapy at screening defined as a minimum of two sequentially rising prostate-specific antigen (PSA) values (PSA1 \< PSA2 \< PSA3); * The screening PSA (PSA3) must be ≥ 2 μg/L (≥ 2 ng/mL). Exclusion Criteria: * Prior enzalutamide, abiraterone acetate, aminoglutethimide, ketoconazole, radium Ra 223 dichloride or other bone-targeting radionuclides, or cytotoxic chemotherapy in the CRPC setting for the treatment of prostate cancer or participation in a clinical trial of an investigational agent that inhibits the androgen receptor or androgen synthesis (unless treatment was placebo); * Treatment with hormonal therapy (eg, androgen receptor inhibitors, 5-alpha reductase inhibitors) or biologic therapy for prostate cancer (other than LHRH analogue therapy) within 4 weeks before enrollment; * Initiation of new treatment with denosumab, bisphosphonates, or systemic corticosteroids for treatment of prostate cancer within 4 weeks before enrollment; * Use of an investigational agent within 4 weeks before the screening visit; * Radiation therapy to bone within 4 weeks before enrollment; * Use of opiate analgesics for prostate cancer pain within 4 weeks before enrollment; * Screening 99mTc-MDP bone scintigraphy showing a superscan; * Visceral (eg, lung, liver) metastatic disease. Adenopathy is allowed; * Current or previously treated brain metastasis or active leptomeningeal disease; * History of seizure any time in the past for any reason or any condition that may predispose to seizures.