New research is changing how certain colon cancers are treated. The study focuses on patients with stage 3 colon cancer who have a genetic feature called dMMR, which affects about 15% of cases and has traditionally responded poorly to standard chemotherapy.
Researchers found that adding the immunotherapy drug atezolizumab to chemotherapy after surgery reduced the risk of cancer returning or causing death by about 50% compared to chemotherapy alone. The trial included 712 patients in the United States and Germany. Patients received six months of chemotherapy combined with immunotherapy, followed by another six months of immunotherapy alone.
The benefit comes from how immunotherapy works in dMMR tumors. These cancers often contain many immune cells, and atezolizumab helps “unmask” the tumor so the immune system can better attack it. The treatment was also effective in patients with Lynch syndrome, a genetic condition linked to earlier-onset colon cancer.
Based on these results, the National Comprehensive Cancer Network has updated its guidelines, making this combination the new standard treatment for stage 3 dMMR colon cancer, and also recommending it for some high-risk stage 2 patients.