# ATOMIC (Alliance A021502)

Source: https://onco.cc/trials/atomic/  
OnCo record `atomic` (Trial). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

Adding a year of immunotherapy to chemotherapy after surgery halved recurrences in stage III colon cancers with a broken DNA spell-checker.

## Summary

ASCO 2025 plenary: 3-year DFS 86.4% vs 76.6% (HR 0.50). The first phase 3 to show immunotherapy benefit in the adjuvant colon setting; establishes a new standard for the ~10-15% of stage III colon cancers that are dMMR. Whether chemotherapy is needed at all in this group (NICHE-2 logic) is the next question.

## Fields

- Kind: Trial
- Status: positive
- Last checked: 2026-09-07
- Registry id: NCT02912559
- Phase: 3
- Setting: Resected stage III dMMR colon cancer: adjuvant FOLFOX + atezolizumab (12 months) vs FOLFOX
- Sponsor: Alliance / NCI
- Enrolled: 712
- Result: 3-year DFS 86.4% vs 76.6%, HR 0.50.
- Outcomes: Disease-free survival at 3 years: FOLFOX + atezolizumab 86.4 percent vs FOLFOX 76.6 percent, HR 0.5
- Replication: First and only randomised adjuvant IO trial in dMMR colon cancer; consistent in direction with NICHE-2 and the metastatic trials.

## Sources

- ClinicalTrials.gov NCT02912559: https://clinicaltrials.gov/study/NCT02912559
- ASCO 2025 LBA1: https://ascopubs.org/doi/10.1200/JCO.2025.43.17_suppl.LBA1

## Connected records

- cancers: [Colon cancer (adenocarcinoma of the colon)](https://onco.cc/cancers/colon-cancer/), [Colorectal cancer](https://onco.cc/cancers/colorectal/), [Mismatch-repair deficient (MSI-high) colorectal cancer](https://onco.cc/cancers/msi-high-colorectal/)
- technologies: [Immune checkpoint inhibitors](https://onco.cc/technologies/checkpoint-inhibitor/)
- drugs: [Atezolizumab](https://onco.cc/drugs/atezolizumab/), [FOLFOX (5-FU, leucovorin, oxaliplatin)](https://onco.cc/drugs/folfox/)
- companies: [Alliance for Clinical Trials in Oncology](https://onco.cc/companies/alliance-oncology/)
- terms: [Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR)](https://onco.cc/terms/msi/), [Neoadjuvant / adjuvant / perioperative](https://onco.cc/terms/neoadjuvant-adjuvant/)
- trials: [Alliance N0147](https://onco.cc/trials/n0147/), [IDEA collaboration](https://onco.cc/trials/idea-collaboration/), [PETACC-8](https://onco.cc/trials/petacc-8/), [Study of Perioperative Dostarlimab in Participants With Untreated T4N0 or Stage III dMMR/MSI-H Resectable Colon Cancer](https://onco.cc/trials/nct05855200/)
- key papers: [Atezolizumab plus FOLFOX for Stage III Mismatch Repair-Deficient Colon Cancer](https://onco.cc/key-papers/paper-atomic-n-engl-j-med-2026/)
- pairings: [Neoadjuvant checkpoint inhibitor → surgery (or no surgery) in dMMR colorectal cancer](https://onco.cc/pairings/neoadjuvant-io-dmmr/)
- roadmaps: [Colorectal cancer roadmap: from the adenoma-carcinoma sequence and the first screening trials to total mesorectal excision, oxaliplatin, RAS testing, immunotherapy for mismatch repair-deficient disease, ctDNA-guided treatment and organ preservation](https://onco.cc/roadmaps/colorectal-roadmap/)

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