Circulating tumor DNA testing can identify stage 3 patients who may safely receive reduced treatment intensity, international study finds.
A blood test that detects circulating tumor DNA (ctDNA) can help clinicians determine which stage 3 colon cancer patients need chemotherapy after surgery and which can safely receive less intensive treatment, according to results from an international clinical trial published in Nature Medicine.
The DYNAMIC-III study, led by the Walter and Eliza Hall Institute (WEHI), enrolled more than 1000 patients with stage 3 colon cancer across Australia, New Zealand, and Canada. All participants had blood drawn approximately six weeks after surgery to remove their primary colon cancer.
Patients with no detectable ctDNA were classified as low-risk, while those with ctDNA present were deemed high-risk. Participants were then randomly assigned to receive either standard chemotherapy or treatment guided by their ctDNA results. The findings were presented at the European Society of Medical Oncology Congress in Germany.
“ctDNA is a powerful tool that can help guide treatment choices and identify which patients might safely receive less intensive treatment and those who might need to seek alternative options,” says Jeanne Tie, MD, professor at WEHI and medical oncologist at the Peter MacCallum Cancer Centre, in a release.
Strong Outcomes for Low-Risk Patients
Among patients identified as low-risk based on their ctDNA levels, 87% remained cancer-free three years after surgery. These patients were able to safely receive less chemotherapy, resulting in fewer hospitalizations and reduced side effects such as nerve damage, with only slightly lower cancer-free survival rates.
“Right now, we give most stage 3 patients the same chemotherapy, but ctDNA testing can help tailor treatment based on individual risk,” says Tie in a release. “For some patients, this means a less intensive approach may be just as effective while reducing unnecessary toxicity from chemotherapy, such as oxaliplatin, and improving their quality of life.”
By contrast, patients whose ctDNA remained detectable after surgery had a much higher risk of recurrence, with only about half remaining cancer-free at three years. The risk worsened as ctDNA levels rose. For this group, receiving more intensive chemotherapy did not improve results, suggesting new treatment approaches are needed.
Building Evidence for Clinical Implementation
The study was conducted in collaboration with the Canadian Cancer Trials Group, Australasian GI Trials Group, and Peter MacCallum Cancer Centre.
“This study provides the best available prospective evidence of the prognostic value of ctDNA in selecting adjuvant chemotherapy for patients with resected stage 3 colon cancer,” says Jonathan Loree, MD, DYNAMIC-III Canadian study chair and Canadian Cancer Trials Group senior investigator, in a release. “Its results are crucial as we build the evidence needed to move ctDNA into the clinic.”
Colon cancer is the fourth most common cancer in Australia, with more than 15,000 people diagnosed in 2024, according to the researchers.
Photo caption: An illustration of a tumour DNA fragment. The new blood test uses circulating tumour DNA (ctDNA) to precisely identify the stage 3 colon cancer patients who need chemotherapy after surgery.
Photo credit: WEHI
