Nivolumab and Metformin in Patients With Treatment Refractory MSS Colorectal Cancer

This phase II trial studies how well nivolumab and metformin work in treating patients with microsatellite stable (MSS) stage IV colorectal cancer that has not responded to previous treatment. Immunotherapy with monoclonal antibodies, such as nivolumab, may help the body’s immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Metformin is an antidiabetic drug that and may reduce the risk of colorectal cancer development in patients. Giving nivolumab and metformin may work better in treating patients with refractory microsatellite metastatic colorectal cancer.