On October 9, 2026, Roche announced that the US Food and Drug Administration (FDA) had approved Tecentriq (atezolizumab) and Tecentriq Hybreza (atezolizumab and hyaluronidase-tqjs), in combination with a fluoropyrimidine and oxaliplatin, for the adjuvant treatment of stage III deficient DNA mismatch repair (dMMR) colon cancer.
The FDA granted the approvals on October 8, 2026, establishing the first approved immunotherapy-based adjuvant treatment regimen for this patient population. The decision was supported by the phase III ATOMIC trial, which demonstrated a 50% reduction in the hazard of disease recurrence or death with atezolizumab plus chemotherapy compared with chemotherapy alone.
The approval represents the twelfth US indication for Tecentriq and introduces a biomarker-directed immunotherapy option following surgery for patients with stage III dMMR colon cancer.
Commenting on the approval, Levi Garraway, MD, PhD, Roche’s Chief Medical Officer and Head of Global Product Development, stated:
“This approval provides a new adjuvant treatment option for people with stage III dMMR colon cancer who face a high risk of disease recurrence.”
A New Adjuvant Treatment Option
Until now, adjuvant systemic treatment for stage III colon cancer has generally relied on fluoropyrimidine- and oxaliplatin-based chemotherapy, regardless of tumor mismatch repair status.
However, approximately 15% of colon cancers are characterized by dMMR or microsatellite instability-high (MSI-H) status. These tumors have distinct biological characteristics, including increased mutational burden, that provide a rationale for immune checkpoint inhibition. Despite curative-intent surgery and adjuvant chemotherapy, disease recurrence remains a substantial concern in stage III colon cancer. According to Roche, nearly 30% of patients with stage III disease experience recurrence within five years.
The new FDA approval allows the addition of atezolizumab, an anti-PD-L1 monoclonal antibody, to fluoropyrimidine- and oxaliplatin-based chemotherapy in the adjuvant setting.
The approved populations differ by formulation:
- Tecentriq (intravenous atezolizumab): Adults and pediatric patients aged 2 years and older with stage III dMMR colon cancer.
- Tecentriq Hybreza (subcutaneous atezolizumab and hyaluronidase-tqjs): Adults and pediatric patients aged 12 years and older weighing at least 40 kg with stage III dMMR colon cancer.
Frank A. Sinicrope, MD, Professor of Oncology at the Mayo Clinic and US Principal Investigator for the Alliance ATOMIC trial, said:
“Until now, the adjuvant standard of care for stage III colon cancer has not differed based on mismatch repair status. 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.”
Evidence Behind the Approval
The FDA decision was based on findings from ATOMIC (A021502; NCT02912559), an international, randomized, open-label phase III study evaluating atezolizumab in combination with modified FOLFOX6 (mFOLFOX6) after complete surgical resection of stage III dMMR colon cancer.
The trial results were published online on March 25, 2026, in The New England Journal of Medicine, under the title “Atezolizumab plus FOLFOX for Stage III Mismatch Repair–Deficient Colon Cancer,” by Frank A. Sinicrope, Fang-Shu Ou, Dirk Arnold, and colleagues.
The study enrolled 712 patients who were randomized 1:1 to receive:
- Atezolizumab plus mFOLFOX6: Six months of combination treatment, followed by an additional six months of atezolizumab monotherapy.
- mFOLFOX6 alone: Six months of standard adjuvant chemotherapy.
The primary endpoint was disease-free survival (DFS), with overall survival (OS) and adverse events evaluated as secondary endpoints.
ATOMIC was sponsored by the US National Cancer Institute and conducted through the Alliance for Clinical Trials in Oncology, with participation from the German AIO network. Genentech, a member of the Roche Group, supported the study.
ATOMIC Results: Significant Improvement in DFS
At a median follow-up of 40.9 months, the ATOMIC trial met its primary endpoint, demonstrating significantly improved DFS with atezolizumab plus mFOLFOX6 compared with mFOLFOX6 alone.
The published results showed:
- 3-year DFS: 86.3% with atezolizumab plus mFOLFOX6 versus 76.2% with mFOLFOX6 alone.
- Hazard ratio for disease recurrence or death: 0.50 (95% CI, 0.35–0.73; p<0.001).
- Absolute difference in 3-year DFS: 10.1 percentage points in favor of the atezolizumab-containing regimen.
These findings corresponded to a 50% relative reduction in the hazard of recurrence or death, providing the principal efficacy evidence supporting regulatory approval.
However, an overall survival advantage had not been established at the time of the published analysis. Five-year OS was 89.7% with atezolizumab plus mFOLFOX6 versus 87.9% with mFOLFOX6 alone (HR 0.90; 95% CI, 0.55–1.47), with no statistically significant difference between treatment groups.
Longer follow-up will be important for further evaluating survival outcomes.
Safety Profile and Treatment Considerations
The safety profile of atezolizumab plus mFOLFOX6 was generally consistent with the known toxicities of the individual treatments, although severe adverse events were more frequent with the combination.
In the published ATOMIC results, grade 3 or 4 adverse events occurred in 84.1% of patients receiving atezolizumab plus mFOLFOX6 compared with 71.9% receiving chemotherapy alone. Treatment-related grade 3 or 4 adverse events were reported in 72.5% and 61.7% of patients, respectively. Two deaths in the atezolizumab-containing group were considered treatment-related by investigators.
The addition of atezolizumab was also associated with higher rates of certain suspected immune-related adverse events, including hypothyroidism, hyperglycemia, colitis, and maculopapular rash. These safety findings highlight the importance of balancing the demonstrated DFS benefit against treatment-associated toxicity when considering adjuvant immunotherapy.
ATOMIC at ESMO GI 2026: Questions About Treatment Duration
Although the ATOMIC results established the benefit of adding atezolizumab to adjuvant chemotherapy, the optimal duration of chemotherapy and immunotherapy remains an important clinical question.
At the ESMO Gastrointestinal Cancers Congress 2026, Anke Reinacher-Schick presented an exploratory secondary analysis of ATOMIC (abstract 1O) investigating whether treatment duration influenced DFS. Using a six-month landmark analysis, investigators observed that among patients who received at least six cycles of mFOLFOX6, 3-year DFS was 88.2% with atezolizumab plus mFOLFOX6 versus 79.1% with mFOLFOX6 alone (adjusted HR 0.46; 95% CI, 0.29–0.71; p=0.0005).
Among patients who received fewer than six cycles of mFOLFOX6, 3-year DFS was 80.0% versus 79.9%, respectively (adjusted HR 0.85; 95% CI, 0.32–2.29). The analysis also examined atezolizumab duration. Three-year DFS was 84.0% among patients receiving fewer than 12 cycles of atezolizumab and 88.0% among those receiving 12 or more cycles (adjusted HR 0.81; 95% CI, 0.38–1.71; p=0.5807).
However, these were exploratory comparisons based on treatment received rather than randomized treatment-duration assignments. They do not establish the optimal duration of chemotherapy or atezolizumab, nor do they determine whether a shorter CAPOX regimen could provide comparable outcomes.
Regulatory Outlook and Clinical Implications
The FDA approval introduces a new immunotherapy-based adjuvant treatment option for patients with resected stage III dMMR colon cancer, supported by randomized phase III evidence of improved disease-free survival.
It also reinforces the clinical importance of determining mismatch repair status in colon cancer, as dMMR is now a biomarker for selecting an FDA-approved immunotherapy-containing regimen in the postoperative setting.
Roche has stated that it is pursuing additional regulatory filings, including with the European Medicines Agency, to expand access to the treatment outside the United States. While questions remain regarding optimal treatment duration, long-term survival outcomes, and the balance between efficacy and toxicity, the ATOMIC findings have established the benefit of adding atezolizumab to mFOLFOX6 for stage III dMMR colon cancer.
The October 2026 FDA approval translates those findings into a new US adjuvant treatment option, marking an important development in biomarker-directed therapy for resected colon cancer.
The full announcement is available on official Roche website.
