Adjuvant Immunotherapy in Stage III dMMR Colon Cancer: A New Standard of Care

Neoadjuvant immunotherapy has revolutionized the treatment of DNA mismatch repair–deficient (dMMR) colorectal cancer, but the role for immunotherapy in the adjuvant setting has been unclear. In the phase 3 ATOMIC trial, 712 patients with resected stage III dMMR colon cancer were randomized to receive adjuvant therapy with atezolizumab in addition to fluorouracil/oxaliplatin/leucovorin (mFOLFOX6) for 6 months, followed by an additional 6 months of atezolizumab, or mFOLFOX6 alone for 6 months. Twenty-one percent of patients had germline Lynch syndrome, 54% had clinically high-risk disease, and 37% had N2 nodal stage disease.