A blood test detecting circulating tumor DNA post-surgery can help identify colorectal cancer patients with liver metastases who are most likely to benefit from adjuvant chemotherapy.
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 European Society for Medical Oncology (ESMO) Gastrointestinal Cancers Congress 2026.
The Phase II GALAXY study, led by researchers from Hyogo Medical University and the University of Oxford, found that patients with detectable circulating tumor DNA (ctDNA) after surgery had significantly better outcomes when receiving adjuvant chemotherapy. At four years post-surgery, overall survival for these patients was 65% with chemotherapy compared to 33% without it.
Disease-free survival was 38% for those receiving chemotherapy versus 7% for those who did not. Among patients who underwent upfront surgery, a positive ctDNA test was associated with more than four times the risk of cancer recurrence and more than nine times the risk of death compared to patients with negative results.
“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,” says Per Pfeiffer, MD, PhD, professor of oncology at Odense University Hospital, in a release.
Predicting Recurrence and Survival
The study included 298 patients who had ctDNA measured between two and 10 weeks after surgery using a personalized, tumor-informed blood test. Of these, 191 underwent upfront surgery and 107 received chemotherapy before surgery.
For patients who underwent upfront surgery and had detectable ctDNA, treatment with adjuvant chemotherapy was associated with a 93% reduction in the risk of recurrence. By contrast, patients without detectable ctDNA showed favorable long-term outcomes regardless of whether they received additional chemotherapy after surgery.
For the group that received chemotherapy before surgery, ctDNA remained a strong predictor of recurrence and survival. However, additional chemotherapy after surgery was not associated with improved outcomes for these patients, regardless of their ctDNA status.
Clinical Implications for Laboratorians
Colorectal cancer is the third most common cancer worldwide and the second leading cause of cancer death, with the liver serving as the most common site of metastatic spread. While surgery offers the best chance for long-term survival, microscopic cancer cells often remain, leading many patients to receive chemotherapy despite uncertainty regarding its effectiveness for their specific case.
“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,” says Pfeiffer in a release.
Pfeiffer notes that while the results are promising, the evidence is not yet strong enough for ctDNA to be used routinely outside of clinical trials. Further randomized studies are required before this testing approach becomes standard practice in clinical settings.
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