RAdium-223 and SABR Versus SABR for Oligometastatic Prostate Cancers

Inclusion Criteria: * Patient must have at least one and up to three asymptomatic metastatic tumor(s) of the bone or soft tissue (with at least one bone metastasis) develop within the past 6-months that are ≤ 5.0 cm or \<250 cm3 * Patient must have had their primary tumor treated with surgery and/or radiation. * Histologic confirmation of malignancy (primary or metastatic tumor). * PSADT \<15 months. PSA doubling time (PSADT) will be calculated using as many PSA values that are available from time of relapse (PSA \> 0.2). To calculate PSADT, the Memorial Sloan Kettering Cancer Center Prostate Cancer Prediction Tool will be used. It can be found at the following web site: https://www.mskcc.org/nomograms/prostate/psa-doubling-time. * Patient may have had prior systemic therapy and/or ADT associated with treatment of their primary prostate cancer. Patient may have had ADT associated with salvage radiation therapy (to the primary prostate cancer or pelvis is allowed). * PSA \> 0.5 but \<50. * Testosterone \> 125 ng/dL. * Patient must be ≥ 18 years of age. * Patient must have a life expectancy ≥ 12 months. * Patient must have an ECOG performance status ≤ 2. * Patient must have normal organ and marrow function as defined as: Before the first administration of Xofigo, the absolute neutrophil count (ANC) should be ≥ 1.5 x 109/L, the platelet count ≥ 100 x 109/L and hemoglobin ≥ 10 g/dL. \* Patient must have the ability to understand and the willingness to sign a written informed consent document. Exclusion Criteria: * No more than 3 years of ADT is allowed, with the most recent ADT treatment having occurred greater than 6 months prior to enrollment. * PSMA-PET/MRI or PSMA-PET/CT scan within the past 6 months with results that demonstrate more disease lesions than baseline CT/Bone Scan * Castration-resistant prostate cancer (CRPC). * Spinal cord compression or impending spinal cord compression. * Suspected pulmonary and/or liver metastases (greater \>10 mm in largest axis). * Patient receiving any other investigational agents. * Patient receiving abiraterone and prednisone. * Patient is participating in a concurrent treatment protocol. * Serum creatinine \> 3 times the upper limit of normal. * Total bilirubin \> 3 times the upper limit of normal. * Liver Transaminases \> 5-times the upper limit of normal. * Unable to lie flat during or tolerate PET/MRI, PET/CT or SBRT. * Prior salvage treatment to the primary prostate cancer or pelvis is allowed. * Refusal to sign informed consent.