In a recent study presented at the 2025 American Society of Clinical Oncology Annual meeting, adding immunotherapy to mFOLFOX6 significantly improved disease-free survival in patients with stage III mismatch repair-deficient (dMMR) colon cancer.
ATOMIC Trial: What Was Studied?
Researchers evaluated patients with stage III colon cancer whose tumors are “mismatch repair–deficient” (dMMR), a type of cancer that can be more likely to come back after surgery. The standard treatment is chemotherapy with a regimen called mFOLFOX6 (a combination of oxaliplatin, leucovorin, and fluorouracil).
The ATOMIC trial tested whether adding atezolizumab, an immunotherapy medicine, to this chemotherapy could improve results for these patients. Over 700 patients from more than 300 hospitals took part in the study. All patients had surgery to remove their cancer and had not received chemotherapy or radiation before enrolling in the study. After surgery, patients were randomly assigned to receive either:
- Standard chemotherapy alone (mFOLFOX6)
- Standard chemotherapy plus atezolizumab, followed by 6 more months of atezolizumab alone
Trial Results:
- After 3 years, 86.4% of patients who received the combination treatment were cancer-free, compared to 76.6% of those who received chemotherapy alone.
- This means the new combination reduced the risk of the cancer coming back or death by 50%.
- The benefit was seen in all groups—regardless of age, sex, race, tumor location, or risk level.
- Side effects were similar to what is expected with these medicines and were manageable.
Why Is This Important?
This is the first large study to show that immunotherapy can help prevent colon cancer from coming back after surgery in people with dMMR tumors.
What Should Patients Know?
- If you have stage III colon cancer and your tumor is dMMR, ask your doctor if this new combination treatment might be right for you.
- These results mean more patients can look forward to longer periods without their cancer returning, with a treatment that is safe and effective.
Always discuss your individual treatment options with your cancer care team.
Read More
Immunotherapy Combination Shows Promise for dMMR Colon Cancer
Localized dMMR/MSI Colon Cancer: More Evidence for Neoadjuvant Immunotherapy
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Reference
Sinicrope FA, Ou F-S, Arnold D, et al. Randomized trial of standard chemotherapy alone or combined with atezolizumab as adjuvant therapy for patients with stage III deficient DNA mismatch repair (dMMR) colon cancer (Alliance A021502; ATOMIC). J Clin Oncol. 2025;43(suppl 17):LBA1.
