To evaluate the improvement in the time to progression (TTP) of metastatic prostate cancer after the combined treatment with sipuleucel-T and SABR to metastatic sites, as compared to the historically reported data with the treatment of sipuleucel-T alone. Progression will be evaluated in this study using the modified new international criteria proposed by the Response Evaluation Criteria in Solid Tumors (RECIST 1.1) Committee [JNCI 92(3):205-216, 2000] with modifications suggested by PCWG2 [49] recommendations and as used in the Phase III clinical trial by Kantoff et. al.[10]. Changes in only the largest diameter (one-dimensional measurement) of the tumor lesions are used in the RECIST v1.1 criteria as outlined in http://www.recist.com/.

To evaluate the percentage of participants with Immune response at 6 weeks. Immune response will be measured using ELISpot assay (with PA2024). An immune endpoint will be reached by the patient if a >100% increase in immune response is measured by ANY of the assays.

To evaluate the improvement in the overall survival (OS) of mCRPCa patients after the combined treatment with sipuleucel-T and SABR to metastatic sites, as compared to the historically reported data with the treatment of sipuleucel-T alone. Overall survival (OS) was defined as the duration of time from the start of treatment to the time of death from any cause.

To evaluate the improvement in the progression free survival (PFS) of mCRPCa patients after the combined treatment with sipuleucel-T and SABR to metastatic sites, as compared to the historically reported data with the treatment of sipuleucel-T alone. Progression free survival (PFS) was defined as the length of time from the start of treatment to disease progression or death from any cause.

To evaluate the improvement in the biochemical progression free survival (bPFS) of mCRPCa patients after the combined treatment with sipuleucel-T and SABR to metastatic sites, as compared to the historically reported data with the treatment of sipuleucel-T alone. Biochemical progression free survival was defined as the time from the beginning of treatment to PSA (prostate-specific antigen) disease progression. Biochemical progression was defined as an increase in PSA of > 2 ng/ml from baseline and an increase of > 25% from the baseline value and confirmed by a second measurement more than three weeks later.

To evaluate the improvement in the prostate cancer-specific survival (PCaSS) of mCRPCa patients after the combined treatment with sipuleucel-T and SABR to metastatic sites, as compared to the historically reported data with the treatment of sipuleucel-T alone. Prostate cancer-specific survival was defined as the percentage of patients who had not died from prostate cancer at the time of analysis

To evaluate the adverse events for the first 6 months after completion of radiation therapy associated with Sipuleucel-T when administered in combination with SABR to metastatic sites, as compared to the historically reported data with the treatment of Sipuleucel-T alone. Toxicity will be assessed according to the NCI Common Toxicity Criteria for Adverse Events (CTCAE), version 4.0. Adverse events not specifically defined in the NCI CTCAE will be scored on the Adverse Event log according to the general guidelines provided by the NCI CTCAE and as outlined:

Grade 1: Mild Grade 2: Moderate Grade 3: Severe or medically significant but not immediately life threatening Grade 4: Life threatening consequences Grade 5: Death related to the adverse event

To evaluate the cost effectiveness and health-related quality adjusted life of the combination treatment of SABR and sipuleucel T in patients with mCRPC.

This data was not collected per protocol. The objective in question was intended to be an exploratory objective rather than a primary objective. However, due to an error in protocol modification, this change did not occur.