PET/MR Assessment of Sipuleucel T Treatment for Metastatic Castration Resistant Prostate Cancer

Inclusion Criteria: * Men ≥ 18 years of age * History of prostate cancer treated with androgen deprivation * Serum Testosterone levels \<50 ng/mL * Established asymptomatic or minimally symptomatic metastasis * Eastern Cooperative Oncology Group (ECOG) performance status≤2 * Accept the terms of the imaging modalities and performance at pre-established time points as described in the protocol and consent * Accept the terms for immune-monitoring blood drawing and performance at pre-established time points as described in the protocol and consent * Patients that are on steroids (prednisone up to 10mg daily or hydrocortisone 20 mg daily) alone or in combination with Zytega or ketoconazole prior to enrollment are eligible * Patients that are on steroids for an underlying chronic condition are eligible. (prednisone up to 10 mg daily, dexamethasone \<2 mg daily or fludrocortisone 0.1 mg daily orally) Exclusion Criteria: * Chemotherapy or radiation therapy treatment within 21 days of Sipuleucel-T * ECOG performance status \>2 * Prior treatment with Sipuleucel-T * Patients with a history of another primary malignancy within the last 2 years that was not curatively treated, excluding basal or squamous cell carcinoma of the skin * Patients with known positivity for human immunodeficiency virus (HIV) or hepatitis C; baseline testing for HIV and hepatitis C is not required * Patients with any significant history of non-compliance to medical regimens or with inability to grant a reliable informed consent * Active spinal cord compression.