Blood Test May Predict Which Colorectal Cancer Patients Benefit from Adjuvant Chemotherapy After Liver Metastasis Surgery
Key Insights
The Phase II GALAXY study found ctDNA testing after surgery for colorectal liver metastases strongly predicts which patients benefit from adjuvant chemotherapy.
Among ctDNA-positive patients who had upfront surgery, adjuvant chemotherapy was associated with 65% vs 33% four-year overall survival and a 93% reduction in recurrence risk.
Patients without detectable ctDNA had favorable outcomes regardless of adjuvant chemotherapy, suggesting the test could spare some from unnecessary treatment.
A blood test measuring circulating tumour DNA (search) (ctDNA) may help identify which patients with colorectal cancer (search) that has spread to the liver are most likely to benefit from chemotherapy after surgery, according to findings from the Phase II GALAXY study presented at the ESMO Gastrointestinal Cancers Congress 2026.
The study, led by researchers from Hyogo Medical University in Japan with collaborators including the University of Oxford, UK, demonstrated that among patients who underwent upfront surgery and had detectable ctDNA after the procedure, those who received adjuvant chemotherapy had markedly better outcomes than those who did not.
At four years after surgery, overall survival was 65% for ctDNA-positive patients who received adjuvant chemotherapy, compared with 33% for those who did not. Disease-free survival showed an even starker contrast: 38% versus 7%, respectively.
The Clinical Challenge in Colorectal Liver Metastases
Colorectal cancer (search) 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, microscopic cancer cells can remain after the procedure, leading many patients to receive adjuvant chemotherapy despite considerable uncertainty over who is most likely to benefit.
Professor Per Pfeiffer, Professor of Oncology at Odense University Hospital, Denmark, who was not involved in the study, underscored the current treatment dilemma: "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."
Study Design and Key Findings
The GALAXY study included 298 patients who underwent surgery for colorectal liver metastases and had ctDNA measured between two and 10 weeks after surgery using a personalized, tumor-informed blood test. Of these participants, 191 underwent upfront surgery, while 107 received neoadjuvant chemotherapy before surgery. The groups were analyzed separately because previous treatment may influence ctDNA results and subsequent benefit from additional chemotherapy.
Among patients who underwent upfront surgery, detectable ctDNA was strongly associated with poorer 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 with those whose ctDNA test was negative.
Crucially, among patients with detectable ctDNA who underwent upfront surgery, those who received adjuvant chemotherapy had substantially better outcomes than those who did not. Treatment was associated with a markedly lower risk of cancer recurrence and death, including a 93% reduction in the risk of recurrence.
By contrast, patients without detectable ctDNA had favourable long-term outcomes regardless of whether they received adjuvant chemotherapy, suggesting ctDNA may help identify which patients are most likely to benefit from additional treatment after surgery.
Differential Findings in the Neoadjuvant Group
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, highlighting the importance of treatment context when interpreting ctDNA results.
Expert Perspective and Next Steps
Professor Pfeiffer offered a measured assessment of the findings: "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."
The results add to a growing body of evidence supporting the use of ctDNA as a biomarker for guiding adjuvant treatment decisions in colorectal cancer (search), though prospective randomized validation remains the critical next step before clinical implementation.