Blood tests could help identify which patients with colorectal cancer that has spread to the liver are most likely to benefit from postoperative chemotherapy, according to research presented today at the ESMO Gastrointestinal Cancer Conference 2026.
The Phase II GALAXY study was led by researchers at Hyogo School of Medicine in Japan and collaborators including the University of Oxford in the UK. The study found that among patients who underwent upfront surgery and had circulating tumor DNA (ctDNA) detected postoperatively, those who received adjuvant chemotherapy had a significantly better prognosis than those who did not. At 4 years after surgery, overall survival was 33% versus 65% and disease-free survival was 7% versus 38%. The findings suggest that ctDNA may help identify patients most likely to benefit from postoperative adjuvant chemotherapy.
Colorectal cancer is the third most common cancer and the second leading cause of cancer death worldwide. The liver is the most common site for metastasis. Surgery has the best chance of long-term survival, but microscopic cancer cells can remain after surgery, so many patients receive adjuvant chemotherapy despite uncertainty about who will benefit most.
Professor Per Pfeiffer, Professor of Oncology at Odense University Hospital in Denmark, who was not involved in the study, commented: “Although only around one in 10 patients are cured with adjuvant therapy, almost all patients experience treatment-related side effects. We hope that ctDNA will help us better identify which patients are most likely to benefit from adjuvant chemotherapy.”
The study included 298 patients who underwent surgery for colorectal liver metastases and had their ctDNA measured between two and 10 weeks postoperatively using a tumor-based personalized blood test. Of these, 191 underwent prior surgery and 107 received neoadjuvant chemotherapy before surgery. Groups were analyzed separately as previous treatment may influence ctDNA results and subsequent benefit from additional chemotherapy.
Among patients who underwent prior surgery, detectable ctDNA was strongly associated with poor outcome. Patients with a positive ctDNA test had a more than four times higher risk of cancer recurrence and a nine times higher risk of death than patients with a negative ctDNA test.
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 found to significantly reduce the risk of cancer recurrence and death, including a 93% reduction in the risk of cancer recurrence.
In contrast, patients without detectable ctDNA had good long-term outcomes, regardless of whether they received adjuvant chemotherapy. This suggests that ctDNA may help identify which patients are most likely to benefit from additional treatment after surgery.
In 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 outcome, regardless of ctDNA status.
Professor Pfeiffer added: ”These findings are promising because they suggest that ctDNA could help doctors identify patients most likely to benefit from chemotherapy after surgery, potentially omitting unnecessary treatments for other patients. However, the evidence is not yet sufficient to routinely use ctDNA outside of clinical trials, and further studies, preferably randomized, are needed before this approach becomes standard practice.. ”
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European Society of Medical Oncology (ESMO)
