FDA Approves Atezolizumab Plus Chemotherapy for Adjuvant Treatment of Stage III dMMR Colon Cancer

Clinical Summary:

• Regulatory Update: The FDA has approved intravenous atezolizumab plus fluoropyrimidine- and oxaliplatin-based chemotherapy for the adjuvant treatment of stage III dMMR colon cancer in adults and pediatric patients aged 2 years and older. Subcutaneous atezolizumab and hyaluronidase was also approved for adults and pediatric patients aged 12 years and older weighing at least 40 kg. 
• Key Outcomes: In the ATOMIC trial, the addition of atezolizumab to mFOLFOX6 significantly improved disease-free survival (DFS) compared with mFOLFOX6 alone, reducing the risk of disease recurrence or death by 50%. Median DFS was not reached in either treatment arm.
• Clinical Relevance: This approval introduces PD-L1 inhibition into the adjuvant treatment setting for stage III dMMR colon cancer, establishing an additional postoperative treatment strategy supported by improved DFS and expanding administration options through intravenous and subcutaneous formulations. 

Based on results from the ATOMIC trial, the US Food and Drug Administration (FDA) has approved atezolizumab (Tecentriq; Genentech) in combination with fluoropyrimidine- and oxaliplatin-based chemotherapy for the adjuvant treatment of adults and pediatric patients aged 2 years and older with stage III mismatch repair deficient (dMMR) colon cancer. 

The FDA also approved subcutaneous atezolizumab and hyaluronidase (Tecentriq Hybreza; Genentech) in combination with a fluoropyrimidine and oxaliplatin for adults and pediatric patients aged 12 years and older weighing at least 40 kg with stage III dMMR colon cancer.

In this multicenter, open-label, active-controlled trial, researchers enrolled 712 patients, including 711 adults and 1 pediatric patient, with stage III dMMR colon cancer who had undergone complete resection of the primary tumor, with no evidence of residual lymph node involvement or metastatic disease. 

Patients were randomized 1:1 to receive either atezolizumab plus modified fluorouracil, leucovorin, and oxaliplatin (mFOLFOX6) for 12 cycles followed by 6 months of atezolizumab monotherapy or mFOLFOX6 alone for 12 cycles. The primary end point was investigator-assessed disease-free survival (DFS). 

At analysis, the addition of atezolizumab significantly improved DFS compared with mFOLFOX6 alone, corresponding to a 50% reduction in the risk of disease recurrence or death (hazard ratio [HR], 0.5; 95% confidence interval [CI], 0.35 to 0.73; P = .0001). Median DFS was not reached in either treatment arm. 

For adults, receiving intravenous atezolizumab, the recommended doses are 840 mg every 2 weeks, 1200 mg every 3 weeks, or 1680 mg every 4 weeks in combination with chemotherapy for 6 months, followed by atezolizumab monotherapy for an additional 6 months or until disease recurrence or unacceptable toxicity. 

For pediatric patients, the recommended intravenous doses are 10 mg/kg, up to a maximum of 840 mg, every 2 weeks or 15 mg/kg, up to a maximum of 1200 mg, every 3 weeks. Treatment is administered with chemotherapy for 6 months, followed by atezolizumab monotherapy for 6 months or until disease recurrence or unacceptable toxicity.

For adults and eligible pediatric patients receiving subcutaneous atezolizumab and hyaluronidase, the recommended regimen is a 15 mL injection containing 1875 mg of atezolizumab and 30,000 units of hyaluronidase every 3 weeks.  Treatment is administered with chemotherapy for 6 months, followed by subcutaneous atezolizumab and hyaluronidase monotherapy for an additional 6 months or until disease recurrence or unacceptable toxicity. 

The recommended subcutaneous dose has not been established for pediatric patients younger than 12 years or those aged 12 years and older weighing less than 40 kg.

The prescribing information for atezolizumab includes warnings and precautions for immune-mediated adverse reactions, infusion-related reactions, complications of allogeneic hematopoietic stem cell transplantation, and embryo-fetal toxicity.

The approvals establish atezolizumab-based adjuvant treatment as an option for patients with stage III dMMR colon cancer following surgical resection, supported by the significant DFS improvement demonstrated in ATOMIC. The availability of intravenous and subcutaneous formulations also provides additional administration options for eligible patients.

Source:

US Food and Drug Administration. FDA approves atezolizumab in combination with chemotherapy for Stage III mismatch repair deficient colon cancer. Accessed on: October 8, 2026. https://www.fda.gov/drugs/resources-information-approved-drugs/fda-approves-atezolizumab-combination-chemotherapy-stage-iii-mismatch-repair-deficient-colon-cancer