Colon cancer patients with negative circulating tumour DNA results can receive less intensive treatment Monday, October 20, 2025 Results from the primary analysis of the ctDNA-negative cohort from the international DYNAMIC-III (CO.29) clinical trial were presented during the Presidential Symposium of the European Society for Medical Oncology Congress in Berlin, Germany and simultaneously published in Nature Magazine. The study demonstrated that a simple blood test detecting circulating tumour DNA (ctDNA) may help physicians make more personalized treatment decisions for people with advanced colon cancer. “For many patients, the prospect of chemotherapy is daunting,” says DYNAMIC-III Australian Study Chair and oncologist at Peter Mac, Professor Jeanne Tie. “Our study shows that if no tumour DNA is detected after surgery, patients may do just as well with less intensive chemotherapy – this means fewer side effects, less disruption to daily life, and more time living well after cancer.”Researchers found that circulating tumour DNA (ctDNA)—fragments of cancer DNA that can be detected in the blood — is a powerful tool to guide treatment after surgery. By identifying whether microscopic cancer cells remain in the body, the ctDNA test helps determine which patients are most likely to benefit from additional chemotherapy and which can safely avoid it.“This study provides the best available prospective evidence of the prognostic value of ctDNA in selecting adjuvant chemotherapy for patients with resected stage III colon cancer and crucial as we build the evidence needed to move ctDNA into the clinic,” says Dr. Jonathan Loree the CO29 Canadian study chair, medical oncologist at BC Cancer and CCTG senior investigator.The DYNAMIC-III (CO.29) study was led by the Australasian Gastro-Intestinal Trials Group (AGITG) in collaboration with the Canadian Cancer Trials Group (CCTG). Between October 2017 and April 2023, 1,002 patients were randomised with 66 sites open across Australia, Aotearoa New Zealand, and Canada—international collaboration was crucial to the recruitment success of this trial. "The trial represents the most recent success story of the more the 20-year AGITG and CCTG collaboration—this important trial will inform international clinical practice and advance the science regarding the use of circulating tumour DNA testing in colon cancer," says Dr. Chris O’Callaghan, CCTG senior investigator.Funding for this international collaboration was provided by the Canadian Cancer Society, the Canadian Institutes of Health Research and the Marcus Foundation in Australia.Nature Medicine publication >Link to the press release > Dr. Jeanne Tie, DYNAMIC-III (CO29) study chair Dr. Jonathan Loree, CO29 Canadian study chair Chris O’Callaghan, CCTG senior investigator
