Immunotherapy after surgery for stage III mismatch-repair-deficient colon cancer
Adding atezolizumab to chemotherapy halved the risk of recurrence or death.
What studies found
In the randomized ATOMIC trial of 712 patients with stage III dMMR colon cancer removed by surgery, atezolizumab with FOLFOX chemotherapy, followed by six months of atezolizumab alone, halved the risk of the cancer returning or death compared with chemotherapy alone (hazard ratio 0.50). The FDA approved it on October 8, 2026.
The catch
Most patients in both groups had not relapsed when results were reported, and overall survival has not been reported. Immune-related side effects can be serious.
What to do
If you have stage III colon cancer, ask whether your tumor was tested for MMR or MSI status before chemotherapy starts.
Sources
Rung 4 of 5, Strong: At least one large randomized trial, or very large consistent studies, on this exact question. How we score
Step by step
For the whole picture, from prevention and screening to treatment and life after, see the colorectal cancer page.
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