Research regarding a blood test to predict chemotherapy benefits for colorectal cancer patients was presented at the ESMO Gastrointestinal Cancers Congress 2026. The findings from the Phase II GALAXY study indicate the test can identify patients who derive improved outcomes from chemotherapy following surgery.

The study, led by researchers from Hyogo Medical University in Japan with collaborators including the University of Oxford in the U.K., included 298 patients who had undergone surgery for colorectal liver metastases. Of the 298 patients, 191 underwent upfront surgery, while 107 received neoadjuvant chemotherapy before surgery. Patients in the study had their ctDNA measured between two and 10 weeks post-surgery through a personalized, tumor-informed blood test.

Among patients who underwent upfront surgery and had detectable circulating tumour DNA (ctDNA) after the procedure, those who received adjuvant chemotherapy demonstrated better outcomes. For patients with detectable ctDNA who underwent upfront surgery, adjuvant chemotherapy was associated with a 93% reduction in the risk of recurrence. 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 with a negative ctDNA test. Conversely, patients without detectable ctDNA had favourable long-term outcomes regardless of whether they received adjuvant chemotherapy.

At four years following surgery, overall survival was 65% for patients with detectable ctDNA who received adjuvant chemotherapy, compared with 33% for those who did not. Disease-free survival at four years post-surgery was 38% for patients with detectable ctDNA who received adjuvant chemotherapy, in contrast to 7% for those who did not. For patients receiving chemotherapy before surgery, ctDNA remained a predictor of recurrence and survival, but additional chemotherapy after surgery was not associated with improved outcomes regardless of ctDNA status.

"Only around 1 in 10 patients is cured by adjuvant therapy, yet almost all patients experience treatment-related side effects," said Per Pfeiffer, Professor of Oncology at Odense University Hospital. "We hope ctDNA can help better identify which patients are most likely to benefit from adjuvant chemotherapy." He 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, Pfeiffer stated, "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."

Why It Matters

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 for colorectal cancer. The findings suggest a potential method to personalize treatment decisions for colorectal cancer patients, by identifying those who would benefit from adjuvant chemotherapy based on ctDNA status.