Imaging Biomarkers to Validate Response in Enzalutamide-Treated mCRPC

Inclusion Criteria: * Histologically proven adenocarcinoma of the prostate. * Identifiable prostate cancer-related osseous metastases on bone scan or NaF PET/CT in the vertebral body, pelvis or other bone. Such lesions must be amenable to serial NaF PET/CT imaging. Preference will be given to subjects with multiple lesions that can be imaged in one image acquisition session to obtain maximal information as well as locations of lesions amenable to bone biopsies. * Patients must be starting enzalutamide for treatment of metastatic castrate-resistant prostate, with cycle 1 day 1 occurring within 14 days after the first baseline NaF PET/CT. Subjects will be allowed to receive enzalutamide treatment on a concurrent study as long as the enzalutamide treatment study does not prohibit concurrent participation. * Men of all races and ethnic groups of age ≥18 years. * The effects of NaF on the developing human fetus are unknown. For this reason and because radiopharmaceuticals used for diagnostic imaging and other therapeutic agents and imaging procedures used in this trial may be or are known to be teratogenic, men must agree to use adequate contraception (hormonal or barrier method of birth control; abstinence) prior to study entry and for the duration of study participation. Should a woman become pregnant or suspect she is pregnant while her partner is participating in this study, she should inform her treating physician immediately. * Patients must be able to comply with all study procedures, including having both the ability and willingness to lie flat for ≥ 30 minutes during imaging and undergo bone biopsies. * Patients must have both the ability to understand and the willingness to sign a written informed consent document. Exclusion Criteria: * Known bleeding diathesis or on therapeutic anticoagulants (warfarin, low-molecular heparin, heparin analogues) that would increase risk of complications from bone biopsies. * History of allergic reactions attributed to compounds of similar chemical or biologic composition to sodium fluoride F-18 (NaF).