The FDA has approved atezolizumab (Tecentriq) in combination with chemotherapy for patients with stage III colon cancer that has mismatch repair–deficient (dMMR) tumors. The decision, which was made public on October 8, 2026, introduces a new treatment option for patients who have undergone surgery and remain at risk of cancer recurrence.
The approval also covers a subcutaneous atezolizumab plus hyaluronidase-tqjs (Tecentriq Hybreza); both formulations of atezolizumab are administered with chemotherapy containing a fluoropyrimidine and oxaliplatin.
Understanding the Role of dMMR
Approximately 15% of colon cancers have dMMR or microsatellite instability-high (MSI-H) tumors. These tumors may be particularly responsive to immunotherapy, which helps the immune system recognize and attack cancer cells.
Atezolizumab works by blocking PD-L1, a protein that can prevent immune cells from effectively targeting cancer. Its use following surgery represents an important development in tailoring colon cancer treatment according to tumor biology.
Clinical Trial Findings
The approval was based on findings from the phase 3 ATOMIC trial, which enrolled 712 patients with stage III dMMR colon cancer following surgical removal of their tumors.
Participants received either standard mFOLFOX6 chemotherapy or the same chemotherapy combined with atezolizumab, followed by an additional six months of atezolizumab alone.
At three years, approximately 86% of patients receiving the combination remained free of cancer recurrence or death, compared with 76% of those receiving chemotherapy alone.
Overall, adding atezolizumab was associated with a 50% relative reduction in the risk of recurrence or death. Although these findings demonstrate a meaningful improvement in disease-free survival, longer-term follow-up will help clarify the treatment’s impact on overall survival.
Implications for Patient Care
The new regimen expands options for patients with stage III dMMR colon cancer, emphasizing the importance of biomarker testing when developing individualized treatment plans.
“Until now, the adjuvant standard of care for stage III colon cancer has not differed based on [MMR] status,” said Frank Sinicrope, MD, Professor of Oncology, Mayo Clinic, and principal investigator for the ATOMIC trial in a press statement released by Roche.
“This milestone represents an important therapeutic advance that leverages immunotherapy to target the specific biology of dMMR stage III colon cancer after surgical resection. By reducing the risk of disease recurrence or death by 50%, atezolizumab plus chemotherapy is a practice-changing regimen that can improve clinical outcomes of this group of patients living with colon cancer, one of the most common cancers and a leading cause of cancer-related death,” he continued.
The approval also highlights the growing role of immunotherapy in earlier stages of cancer treatment, where preventing recurrence remains a central goal.
Of note, atezolizumab may cause immune-related complications affecting organs such as the lungs, liver, and intestines, requiring careful monitoring throughout treatment.
For the oncology care team, discussing tumor testing results, treatment duration, and potential risks with the patients and their caregivers can help inform decisions about post-surgical care.
Sources
US Food and Drug Administration. FDA approves atezolizumab in combination with chemotherapy for stage III mismatch repair deficient colon cancer. Published October 8, 2026. Accessed October 9, 2026. www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-atezolizumab-combination-chemotherapy-stage-iii-mismatch-repair-deficient-colon-cancer
The ASCO Post. FDA approves atezolizumab in combination with chemotherapy for stage III dMMR colon cancer. Published October 9, 2026. Accessed October 9, 2026. https://ascopost.com/news/october-2026/fda-approves-atezolizumab-in-combination-with-chemotherapy-for-stage-iii-dmmr-colon-cancer
Roche. FDA approves Roche’s Tecentriq in combination with a fluoropyrimidine and oxaliplatin for the adjuvant treatment of a certain type of stage III colon cancer. Published October 8, 2026. Accessed October 9, 2026. www.roche.com/media/releases/med-cor-2026-10-09