Immunotherapy & Chemotherapy for Stage 3 Colon Cancer
- A new study reveals that adding immunotherapy to chemotherapy after surgery significantly improves outcomes for stage 3 colon cancer patients with deficient DNA mismatch repair (dMMR).
- Colon cancer is a common cancer in the U.S., and while screening efforts have improved detection, treatment advancements have been slower.
- Frank Sinicrope, an oncologist who led the study, said the findings represent a major advance in treating dMMR stage 3 colon cancer.
Immunotherapy Boosts Chemotherapy for Stage 3 Colon Cancer
Updated June 01,2025
A new study reveals that adding immunotherapy to chemotherapy after surgery significantly improves outcomes for stage 3 colon cancer patients with deficient DNA mismatch repair (dMMR). The Mayo Clinic Complete Cancer Center-led research, presented at the 2025 american Society of Clinical Oncology (ASCO) Annual Meeting, showed a 50% reduction in cancer recurrence and death compared to chemotherapy alone.
Colon cancer is a common cancer in the U.S., and while screening efforts have improved detection, treatment advancements have been slower. The study focused on the roughly 15% of colon cancer patients who exhibit dMMR, a genetic makeup that makes tumors less responsive to chemotherapy.
Dr. Frank Sinicrope, an oncologist who led the study, said the findings represent a major advance in treating dMMR stage 3 colon cancer. He added that the new treatment regimen can reduce the risk of recurrence and improve survival chances.
The clinical trial involved 712 patients with surgically removed dMMR stage 3 colon cancer and cancer cells in their lymph nodes. Patients received six months of chemotherapy combined with the immune checkpoint inhibitor atezolizumab,followed by six months of atezolizumab alone. Atezolizumab activates the immune system to target and kill cancer cells.
“The findings from our study represent a major advance in the adjuvant treatment of dMMR stage 3 colon cancer and will now change the treatment for this type of cancer,” said Dr. Sinicrope.
Sinicrope’s earlier research indicated that tumors in dMMR patients exhibit increased inflammatory cells, including those targeted by immune checkpoint inhibitors. This observation led to the idea of using these inhibitors to enhance the immune system’s ability to attack cancer cells.
Based on the study’s results, Sinicrope recommends the combination of immunotherapy and chemotherapy as the new standard treatment for stage 3 deficient mismatch repair colon cancer. The research team plans to present this recommendation to the National Comprehensive Cancer Network.
The study also included patients with Lynch syndrome,the most common form of hereditary colon cancer,as these patients can have tumors that show deficient mismatch repair (dMMR).
“We’re changing the paradigm in colon cancer treatment. By using immunotherapy at earlier stages of disease, we are achieving meaningful benefits for our patients,” said Dr. Sinicrope.
What’s next
Researchers hope this new treatment approach will be rapidly adopted, improving outcomes for colon cancer patients with dMMR.Further studies may explore the effectiveness of this combination in other stages of colon cancer.