Docetaxel and PROSTVAC for Metastatic Castration-Sensitive Prostate Cancer

Background: * A phase III trial demonstrated that combining docetaxel and androgen deprivation therapy (ADT) significantly improved survival (57.6 vs 44.0 months (hazard ration (HR)=0.56, (0.44-0.70), p \<0.0001) for men with metastatic castration sensitive prostate cancer (mCSPC). * PROSTVAC (developed by the National Cancer Institute \[NCI\] and licensed to Bavarian Nordic Immunotherapeutics, Mountain View, California (CA) is a therapeutic cancer vaccine for prostate cancer. * Preclinical and clinical studies support the potential synergy in the combination of docetaxel and PROSTVAC. The potential to combine docetaxel with vaccine in mCSPC could improve upon the survival advantage that has been previously seen. Objectives: Primary -To determine if PROSTVAC combined with docetaxel is able to induce greater antigen spreading (i.e. a broader immune response) with greater associated response score compared to docetaxel alone after 19 weeks. Key Eligibility Criteria: * Must have castrate sensitive prostate cancer (rising PSA and testosterone over 100) or is within 134 days of starting ADT (Arm A or B) or within 28 days of start ADT (Arm C) * Histopathological confirmation of prostate cancer * Patients must have metastatic disease * Patients must have a performance status of 0 to 2 according to the Eastern Cooperative Oncology Group (ECOG) criteria * Patients must have adequate bone marrow, hepatic, and renal function Design * This is a randomized trial of ADT followed by simultaneous docetaxel 75 mg/m(2) every (q)3 weeks x 6 cycles + PROSTVAC q3 weeks x 6 cycles versus ADT followed by sequential docetaxel 75 mg/m(2) q3 weeks x 6 cycles followed by PROSTVAC q3 weeks x 6 cycles in men with newly diagnosed mCSPC. * Patients who have not started ADT or who have been on ADT 28 days or fewer will be assigned to treatment with PROSTVAC for 4 - 6 injections followed by docetaxel 75 mg/m\^2 q3 weeks x 6 cycles.