Nivolumab With or Without Ipilimumab in Treating Patients With Gastrointestinal Stromal Tumor That Is Metastatic or Cannot Be Removed by Surgery

This randomized phase II trial studies how well nivolumab with or without ipilimumab works in treating patients with gastrointestinal stromal tumor that has spread to other places in the body or cannot be removed by surgery. Monoclonal antibodies, such as nivolumab and ipilimumab, interfere with the ability of tumor cells to grow and spread.