A Study of Stereotactic Body Radiation Therapy and Radium (Ra-223) Dichloride in Prostate Cancer That Has Spread to the Bones

Inclusion Criteria: * Biopsy proven prostate adenocarcinoma * ≥ 18 years old * Primary prostate tumor must have been treated with prior prostatectomy or definitive radiotherapy * Men with prior salvage radiotherapy to the prostate bed and/or locoregional lymph nodes are eligible assuming normalization of testosterone * Negative multi-parametric MRI and/or negative biopsy of the prostate (or prostate bed) within 60 days of enrollment * Pre-enrollment imaging (any bone imaging modality per institutional standard of care) demonstrates oligometastatic disease with 1-3 discrete metastatic lesions of the bone performed within 60 days of study enrollment; screening PSMA PET confirming 1-3 sites of oligometastatic disease performed within 60 days of enrollment. * All bony oligometastatic sites must be deemed appropriate to receive 3 fraction SBRT to a dose of 9 Gy x 3 at best judgment of treating radiation oncologist * Prostate specific antigen (PSA) ≥ 0.5 ng/mL but ≤ 50 ng/mL * Patients may have had prior androgen deprivation therapy (ADT) but must have normal testosterone levels (\>100 ng/dL) at time of enrollment; patients with baseline low testosterone but no ADT exposure are eligible * Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2 * Subjects who have not had surgical removal of their prostate and have a partner of child bearing potential must agree to use condoms beginning at the signing of the consent until at least 6 months after the last dose of study drug…