Medicine

Immunotherapy significantly improves outcomes for colon cancer

Results from the pivotal Phase III Alliance ATOMIC A021502 trial, now published in The New England Journal of Medicine, demonstrate that adding the immunotherapy atezolizumab (Tecentriq®) to standard adjuvant chemotherapy significantly improves outcomes for patients with resected stage III colon cancer with deficient DNA mismatch repair (dMMR). The study showed a 50 per cent reduction in the risk of disease recurrence or death compared with chemotherapy alone, establishing a new standard of care for this biologically distinct subgroup.

At three years, 86.3 per cent of patients treated with atezolizumab in combination with FOLFOX chemotherapy remained disease-free, compared with 76.2 per cent of patients receiving chemotherapy alone (hazard ratio for recurrence or death, 0.50; 95 per cent confidence interval, 0.35–0.73). After a median follow-up of 40.9 months, 127 disease-free survival events were observed.

Between September 2017 and January 2023, the ATOMIC trial enrolled 712 patients following curative resection of stage III dMMR colon cancer. Participants were randomized to receive six months of standard FOLFOX chemotherapy alone or FOLFOX combined with atezolizumab, followed by an additional six months of atezolizumab monotherapy.

The findings were first presented as Late-Breaking Abstract #1 during the Plenary Session of the 2025 Annual Meeting of the American Society of Clinical Oncology (ASCO) and have now been peer-reviewed and published in The New England Journal of Medicine.

The global study in the U.S. was sponsored by the U.S. National Cancer Institute (NCI), part of the National Institutes of Health, and led by the Alliance for Clinical Trials in Oncology with participation from other NCI-funded National Clinical Trials Network (NCTN) groups. Genentech, a member of the Roche Group, provided support for the study through a Cooperative Research and Development Agreement bewteen NCI and Genentech. The trial was led globally by Frank A. Sinicrope, MD, Professor of Oncology at the Mayo Clinic and U.S. Principal Investigator within the Alliance.

German participation in this major international academic collaboration was enabled through close cooperation between the Alliance and the AIO (Arbeitsgemeinschaft Internistische Onkologie) of the German Cancer Society (Deutsche Krebsgesellschaft, DKG), under the national leadership of Professor Anke Reinacher-Schick (Ruhr University Bochum). AIO-affiliated study sites enrolled patients during the later recruitment phase, ensuring access for eligible patients in Germany.

“The ATOMIC trial represents a pivotal advancement in the adjuvant treatment of stage III dMMR colon cancer,” said Professor Anke Reinacher-Schick. “For the first time, immunotherapy has demonstrated a clear and clinically meaningful benefit in early-stage dMMR disease, establishing a new therapeutic standard. In Germany, rapid identification of eligible patients was facilitated by AIO’s COLOPREDICT registry, which played a key role in screening and timely enrollment.”

“This study demonstrates how international academic collaboration can translate biomarker-driven science into practice-changing clinical results,” said Professor Dirk Arnold (Asklepios Tumorzentrum Hamburg, AK Altona; AIO/GI Oncology). “The close partnership between German and U.S. investigators highlights the strength of academic research networks in advancing precision oncology.”

“This success underscores the power of multinational, academically driven research partnerships,” added Dr. Mischo Kursar, Managing Director of AIO-Studien-gGmbH. “As German Sponsor Representative, AIO-Studien-gGmbH enabled AIO sites to participate fully in this defining global trial and showcased the strength of Germany’s clinical research infrastructure.”

The clinical relevance of ATOMIC is further reflected by the inclusion of its findings in the latest National Comprehensive Cancer Network (NCCN) guidelines, reinforcing the role of immunotherapy-based adjuvant treatment strategies in high-risk patient populations.

AIO (Arbeitsgemeinschaft Internistische Onkologie) is a leading cooperative academic oncology working group in Germany, focused on advancing high-quality, academically led cancer research. The AIO-Studien-gGmbH serves as its operational and legal entity for clinical trial execution and international partnerships. For more information about the ATOMIC study, visit ClinicalTrials.gov/NCT02912559.