FOcal Radiation for Oligometastatic Castration-rEsistant Prostate Cancer (FORCE)

Inclusion Criteria: * Subjects must have biopsy-confirmed adenocarcinoma of the prostate * Subjects must discontinue any prior systemic therapies (excluding GnRH agonist/antagonists) without PSA withdrawal effects if using first generation anti-androgens. Luteinizing hormone-releasing hormone (LHRH) analogues must be continued if they have not undergone orchiectomy. (Subjects who recently started systemic therapy for metastatic castration-resistant prostate cancer (mCRPC) are eligible to enroll if new therapy was started ≤ 14 days to consent date.) * Subjects must have progressive metastatic castration-resistant prostate cancer based on at least one of the following criteria while having castrate levels (\<50 ng/dL) of testosterone: * A) PSA progression defined as a 25% increase over baseline value with an increase in the absolute value of at least 2.0 ng/mL that is confirmed by another PSA level with a minimum of a 1-week interval. * B) Progression of bidimensionally measurable soft tissue or nodal metastasis by CT scan or MRI based on RECIST criteria * C) Progression of bone disease on bone scan as defined by two new lesions arising * Subjects must have oligometastatic prostate cancer, defined as between 1 and ≤5 treatment sites that can be treated within a radiotherapy treatment field. * Subjects must be medically fit to undergo radiotherapy and systemic therapy as determined by the treating physician. * Age ≥ 18 * ECOG ≤ 2 (Eastern Cooperative Oncology Group scoring syst…