Testing the Addition of Radiation Therapy to Immunotherapy for Merkel Cell Carcinoma

This randomized phase II trial studies how well pembrolizumab with or without stereotactic body radiation therapy works in treating patients with Merkel cell cancer that has spread to other places in the body (advanced). Immunotherapy with monoclonal antibodies, such as pembrolizumab, may help the body’s immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Stereotactic body radiation therapy uses special equipment to position a patient and deliver radiation to tumors with high precision. This method can kill tumor cells with fewer doses over a shorter period and cause less damage to normal tissue. Giving pembrolizumab with stereotactic body radiation therapy may work better in treating patients with Merkel cell cancer.