A blood test may help identify which patients with colorectal cancer that has spread to the liver are most likely to benefit from chemotherapy after surgery, according to research presented at the ESMO Gastrointestinal Cancers Congress 2026 on July 3.
The Phase II GALAXY study, led by researchers from Hyogo Medical University in Japan with collaborators including the University of Oxford in the UK, found that among patients who underwent upfront surgery and had detectable circulating tumour DNA (ctDNA) after surgery, those who received adjuvant chemotherapy had better outcomes than those who did not. At four years post-surgery, overall survival was 65% for those receiving chemotherapy compared to 33% for those who did not; disease-free survival was 38% versus 7%. The findings suggest ctDNA could help identify patients most likely to benefit from adjuvant chemotherapy following surgery.
Colorectal cancer is the third most common cancer worldwide and is the second leading cause of cancer death. The liver is cited as the most common site where this type of cancer spreads. Although surgery offers a chance at long-term survival, microscopic cancer cells can remain after surgery, so many patients receive additional chemotherapy despite uncertainty over its effectiveness for all individuals.
Professor Per Pfeiffer, Professor of Oncology at Odense University Hospital in Denmark and not involved in the study, said, "Only around 1 in 10 patients is cured by adjuvant therapy, yet almost all patients experience treatment-related side effects. We hope ctDNA can help better identify which patients are most likely to benefit from adjuvant chemotherapy."
The study included 298 patients undergoing surgery for colorectal liver metastases with ctDNA measured between two and ten weeks after their procedures using a personalized blood test. Of these participants, 191 underwent upfront surgery while another group received neoadjuvant chemotherapy before their operations; groups were analyzed separately due to potential influences on ctDNA results.
Among those who had upfront surgery, detectable ctDNA correlated strongly with poorer outcomes—patients testing positive faced more than four times higher risk of recurrence and more than nine times higher risk of death compared with negative testers. For these high-risk individuals, receiving adjuvant chemotherapy resulted in substantially improved outcomes—including a reported reduction of recurrence risk by up to 93%. By contrast, among those without detectable ctDNA post-surgery or among pre-treated groups regardless of ctDNA status, additional post-operative chemotherapy did not improve outcomes.
Pfeiffer added, "These findings are promising because they suggest ctDNA could help doctors identify which patients are most likely to benefit from chemotherapy after surgery, while potentially sparing others unnecessary treatment. However, the evidence is not yet strong enough for ctDNA to be used routinely outside clinical trials, and further studies, preferably randomised, are needed before this approach becomes standard practice."
