Purpose

This phase III trial studies combination chemotherapy and atezolizumab to see how well it works compared with combination chemotherapy alone in treating patients with stage III colon cancer and deficient deoxyribonucleic acid (DNA) mismatch repair. Drugs used in combination chemotherapy, such as oxaliplatin, leucovorin calcium, and fluorouracil, work in different ways to stop the growth of tumor cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading. Immunotherapy with monoclonal antibodies, such as atezolizumab, may help the body's immune system attack the cancer, and may interfere with the ability of tumor cells to grow and spread. Giving combination chemotherapy with atezolizumab may work better than combination chemotherapy alone in treating patients with colon cancer.