A blood test can help identify which patients with colon cancer that has spread to the liver are more likely to benefit from chemotherapy after surgery, according to research presented today at the ESMO Gastrointestinal Cancers Congress 2026.
The Phase II GALAXY study was conducted by researchers from Japan’s Hyogo Medical University, along with partners such as the University of Oxford, in the United Kingdom. The study found that among patients who underwent upfront surgery and had detectable circulating tumor DNA (ctDNA) after surgery, those who received adjuvant chemotherapy had significantly better outcomes than those who did not. At four years after surgery, overall survival was 65% compared with 33%, while disease-free survival was 38% compared with 7%. The findings suggest that ctDNA could help identify patients who are more likely to benefit from adjuvant chemotherapy after surgery.
Colorectal cancer is the third most common cancer worldwide and the second leading cause of cancer death. The liver is the most common site of metastatic spread. Although surgery offers the best chance of long-term survival, tiny cancer cells can remain after surgery, so many patients receive adjuvant chemotherapy despite uncertainty about who is most likely to benefit.
Professor Per Pfeiffer, Professor of Oncology at Odense University Hospital, Denmark, who was not involved in the study, commented: “Only about 1 in 10 patients are cured with adjuvant therapy, yet almost all patients experience treatment-related side effects. We hope that ctDNA can help better identify patients who are most likely to benefit from adjuvant therapy.”
The study included 298 patients who underwent surgery for colorectal liver metastases and measured ctDNA between two and 10 weeks after surgery using a personalized, tumor-informed blood test. Of these, 191 underwent upfront surgery, while 107 received neoadjuvant chemotherapy before surgery. Groups were analyzed separately because prior treatment may influence ctDNA results and benefit from additional chemotherapy.
Among patients who underwent upfront surgery, detectable ctDNA was strongly associated with worse outcomes. Patients with a positive ctDNA test had more than four times the risk of cancer recurrence and more than nine times the risk of death compared to those whose ctDNA test was negative.
Importantly, among patients with detectable ctDNA who underwent upfront surgery, those who received adjuvant chemotherapy had significantly better outcomes than those who did not. The treatment was associated with a significantly lower risk of cancer recurrence and death, including a 93% reduction in the risk of recurrence.
In contrast, patients without detectable ctDNA had favorable long-term outcomes regardless of whether they received adjuvant chemotherapy, suggesting that ctDNA may help identify patients most likely to benefit from additional treatment after surgery.
Among patients who had already received chemotherapy before surgery, ctDNA remained a strong predictor of recurrence and survival. However, additional chemotherapy after surgery was not associated with improved outcomes regardless of ctDNA status.
Professor Pfeiffer added:These findings are promising because they suggest that ctDNA could help doctors identify which patients are most likely to benefit from chemotherapy after surgery, potentially sparing unnecessary treatments. However, the evidence is not yet strong enough for ctDNA to be used routinely outside of clinical trials, and further studies, preferably randomized, are needed before this approach becomes standard practice..”
