Blood Test Helps Guide Post-Surgical Treatment in Metastatic Colorectal Cancer

The liver is the most frequent site of spread, and although surgery offers the best chance of long-term survival, microscopic disease can persist. Many patients therefore receive adjuvant chemotherapy despite uncertainty about who will benefit. New findings demonstrate that a personalized blood test for circulating tumor DNA can help identify which patients are most likely to benefit after surgery.

Hyogo Medical University led the Phase II GALAXY study evaluating a personalized, tumor-informed blood test that measures circulating tumor DNA (ctDNA) after resection of colorectal liver metastases. The assay was performed between two and 10 weeks following surgery. Investigators assessed whether post-operative ctDNA status could stratify recurrence risk and guide adjuvant chemotherapy decisions.

The study enrolled 298 patients who underwent surgery for colorectal liver metastases. Of these, 191 had upfront surgery and 107 received neoadjuvant chemotherapy before surgery; the cohorts were analyzed separately because prior treatment could influence ctDNA results and subsequent benefit from additional chemotherapy. Detectable ctDNA after upfront surgery was strongly associated with worse outcomes, conferring more than four times the risk of recurrence and more than nine times the risk of death compared with ctDNA-negative status.

Among patients with detectable ctDNA after upfront surgery, adjuvant chemotherapy was associated with substantially improved outcomes. Four years after surgery, overall survival was 65% with adjuvant chemotherapy compared with 33% without, while disease-free survival was 38% versus 7%. Treatment in this ctDNA-positive subgroup was linked to a 93% reduction in recurrence risk. In contrast, patients without detectable ctDNA had favorable long-term outcomes regardless of adjuvant therapy, and in those who had received neoadjuvant chemotherapy before surgery, additional post-operative chemotherapy was not associated with improved outcomes irrespective of ctDNA status.

The findings were presented at the ESMO Gastrointestinal Cancers Congress 2026. The study was conducted by researchers at Hyogo Medical University with collaborators including the University of Oxford. The results suggest ctDNA testing may help identify patients most likely to benefit from adjuvant chemotherapy after surgery.

“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,” said Per Pfeiffer, professor of oncology at Odense University Hospital, Denmark.

“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 randomized, are needed before this approach becomes standard practice,” added Pfeiffer.

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