A blood test detecting circulating tumour DNA (ctDNA) after surgery can identify colorectal cancer patients most likely to benefit from adjuvant chemotherapy, according to research presented at the 2026 ESMO Gastrointestinal Cancers Congress. The Phase II GALAXY study, led by researchers from Hyogo Medical University and collaborators including the University of Oxford, found that patients with detectable ctDNA who received chemotherapy experienced a 93% reduction in the risk of cancer recurrence compared to those who did not.
How ctDNA Testing Influences Post-Surgery Treatment
The GALAXY study suggests that ctDNA serves as a biomarker to guide clinical decisions after surgery for colorectal liver metastases. For patients who underwent upfront surgery, those with detectable ctDNA faced a significantly higher risk of recurrence and death. However, administering adjuvant chemotherapy to these specific patients drastically improved survival rates. Four years post-surgery, patients with detectable ctDNA who received chemotherapy achieved a 65% overall survival rate, compared to 33% for those who did not receive the treatment.
Colorectal cancer remains the third most common cancer globally and the second leading cause of cancer-related deaths. The liver is the most frequent site for metastatic spread, making post-surgical management a critical focus for oncologists.
Why Does ctDNA Status Matter for Patient Outcomes?
According to the study findings, ctDNA status acts as a filter for treatment necessity. Patients who tested negative for ctDNA after surgery showed favorable long-term outcomes regardless of whether they received further chemotherapy. This indicates that a portion of patients may currently be subjected to unnecessary treatment-related side effects. Professor Per Pfeiffer, Professor of Oncology at Odense University Hospital, who was not involved in the study, noted that only about one in 10 patients is cured by adjuvant therapy, highlighting the clinical need for better patient stratification.
Comparing Treatment Pathways: Upfront Surgery vs. Neoadjuvant Chemotherapy
The GALAXY study analyzed 298 patients, divided into two distinct groups based on their treatment history. Of these, 191 underwent upfront surgery, while 107 received neoadjuvant chemotherapy before their operation. The research team separated these groups because previous exposure to chemotherapy can alter ctDNA levels and affect how a patient responds to subsequent rounds of treatment.
| Patient Group | Key Finding |
|---|---|
| Upfront Surgery | Adjuvant chemotherapy significantly reduced recurrence and death. |
| Prior Neoadjuvant Chemotherapy | Post-surgery chemotherapy showed no significant improvement in outcomes. |
What Are the Next Steps for Clinical Adoption?
While the results are promising, the medical community maintains a cautious approach toward routine implementation. Professor Pfeiffer emphasized that current evidence is not yet sufficient to make ctDNA testing a standard of care outside of clinical trials. He noted that further studies, preferably randomised, are required to confirm these findings before they can be widely adopted in oncology clinics worldwide.
If you or a loved one are exploring treatment options for metastatic colorectal cancer, ask your oncologist about the availability of clinical trials involving ctDNA monitoring. Participation in these trials remains the most reliable way to access emerging diagnostic tools.
Frequently Asked Questions
What is circulating tumour DNA (ctDNA)?
ctDNA is small fragments of DNA released by cancer cells into the bloodstream. Measuring these fragments allows doctors to detect the presence of residual microscopic disease after surgery.
Can ctDNA testing replace chemotherapy?
No. The study indicates that ctDNA testing helps identify which patients are most likely to benefit from chemotherapy, potentially sparing those who are unlikely to see a benefit from the toxicity of unnecessary treatment.
Is this test currently standard practice?
Not yet. According to Professor Pfeiffer, further randomized studies are necessary before ctDNA testing is integrated into standard clinical practice for colorectal cancer patients.
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