Stereotactic Body Radiation Therapy With REGN2810 and/or Ipilimumab Before Surgery in Treating Participants With Progressive Advanced or Oligometastatic Prostate Cancer

PRIMARY OBJECTIVES: I. To determine the safety and tolerability for an established effective dose of systemic REGN2810 and intraprostatic ipilimumab with stereotactic body radiation therapy (SBRT) in patients with locally advanced prostate cancer with or without oligometastatic disease. SECONDARY OBJECTIVES: I. To determine overall pathologic response rate after radical prostatectomy. II. To determine prostate‐specific antigen (PSA) progression free survival in men treated with REGN2810 and intraprostatic ipilimumab with SBRT. III. To determine radiographic progression free survival in men treated with REGN2810 and intraprostatic ipilimumab with SBRT. IV. Acute and chronic adverse events (AEs).