Nivolumab and Radiation Therapy or Ipilimumab as Adjuvant Therapy in Treating Patients With Merkel Cell Cancer

This phase I trial studies the side effects and how well nivolumab works when given together with radiation therapy or ipilimumab as adjuvant therapy in treating patients with Merkel cell cancer. Immunotherapy with monoclonal antibodies, such as nivolumab and ipilimumab, may help the body?s immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Radiation therapy uses high energy x-rays, gamma rays, neutrons, protons or other sources to kill tumor cells and shrink tumors. Giving nivolumab with radiation therapy or ipilimumab after surgery may kill any remaining tumor cells.