Results from the Phase 3 ATOMIC trial show that adding atezolizumab to standard chemotherapy significantly lowers the risk of recurrence in patients with resected stage III colon cancer that has deficient DNA mismatch repair (dMMR).
The study found that combining atezolizumab with FOLFOX chemotherapy cut the risk of cancer returning or death by half. Three-year disease-free survival was 86.3% with the combination versus 76.2% with chemotherapy alone. Benefits were seen across all patient groups, including those with high-risk tumors and patients over age 70. Patients received six months of FOLFOX plus atezolizumab, followed by six months of atezolizumab alone.
Side effects were manageable, though severe events were somewhat more common with the combination (84.1% vs. 71.9%). The findings have already led to updates in the NCCN Guidelines, recommending FOLFOX or CAPOX plus atezolizumab as a preferred adjuvant therapy for stage III dMMR colon cancer. The study highlights the importance of testing all colon cancer patients for MMR status, as this determines eligibility for this highly effective post-surgery immunotherapy.
The ATOMIC trial is the first to show that immunotherapy works in the adjuvant setting for dMMR colon cancer, moving a treatment once used only for advanced cases into an earlier stage where curing the disease is the main goal.