ATOMIC (A021502): Adjuvant Atezolizumab in Stage III dMMR Colon Cancer
For healthcare professionals. Educational summary of published literature; not patient-specific medical advice. Always consult the original publication.
- Study / trial name
- ATOMIC (Alliance protocol A021502); NCT02912559
- Population
- Adults (and one pediatric patient) with stage III, mismatch-repair-deficient (dMMR) colon cancer after complete surgical resection of the primary tumor
- Intervention vs. control
- Atezolizumab + mFOLFOX6 for 12 cycles, then atezolizumab monotherapy for 6 months, vs. mFOLFOX6 alone for 12 cycles (randomized 1:1; n=712 per ClinicalTrials.gov actual enrollment, described by FDA as 711 adults plus 1 pediatric patient)
- Primary endpoint & results
- Disease-free survival (investigator-assessed). HR 0.50 (95% CI 0.35–0.73; p=0.0001). Median DFS was not reached in either arm as of the reported analysis.
- Key secondary endpoints
- Not detailed in the sources reviewed for this entry — not reported here to avoid inventing figures.
- Toxicity
- FDA's approval summary lists warnings for immune-mediated adverse reactions, infusion-related reactions, complications of allogeneic hematopoietic stem-cell transplantation, and embryo-fetal toxicity (class effects of checkpoint inhibition). No boxed warning. Specific grade ≥3 adverse-event rates were not captured in the sources reviewed for this entry.
- Practice impact
- First phase 3 evidence supporting adjuvant immune checkpoint inhibition in resected, dMMR colon cancer — a biomarker-defined population previously treated with chemotherapy alone in the adjuvant setting. FDA approved atezolizumab (and its subcutaneous formulation, atezolizumab and hyaluronidase) for this indication on October 8, 2026.
Sources
Primary publication: Sinicrope FA, et al. "Atezolizumab plus FOLFOX for Stage III Mismatch Repair-Deficient Colon Cancer." N Engl J Med. 2026;394(12):1155-1166. DOI: 10.1056/NEJMoa2507874.
Regulatory source: FDA approval notice, October 8, 2026. Trial registry: ClinicalTrials.gov NCT02912559 (Phase 3).
Last reviewed: October 12, 2026
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Summary written by Dr. Zubair Ali. Independent summary; not affiliated with or endorsed by the trial investigators, NEJM, or FDA.