Colorectal cancer is one of the most common cancers in the world and is also one of the leading causes of cancer deaths. It begins in the colon or rectum and can spread to other organs if it is not fully controlled.
The liver is the most common place for colorectal cancer to spread because blood from the intestines flows directly to the liver. When this happens, surgery to remove the liver tumors often offers the best chance of long-term survival. However, even after successful surgery, tiny cancer cells that cannot be seen on scans may remain in the body and later grow into new tumors.
Because of this risk, many patients receive chemotherapy after surgery. This treatment, called adjuvant chemotherapy, aims to destroy any remaining cancer cells.
The problem is that chemotherapy can cause unpleasant side effects, including tiredness, nausea, infections, and nerve damage. Doctors have long wanted a better way to identify which patients are truly likely to benefit from additional treatment.
New research presented at the ESMO Gastrointestinal Cancers Congress 2026 suggests that a simple blood test may help answer this question. The Phase II GALAXY study was led by researchers from Hyogo Medical University in Japan together with international collaborators including the University of Oxford in the United Kingdom.
The study focused on circulating tumor DNA, or ctDNA. When cancer cells die, they release tiny pieces of their DNA into the bloodstream. Sensitive laboratory tests can detect these small fragments. If ctDNA is found after surgery, it may indicate that microscopic cancer cells are still present somewhere in the body.
The researchers studied 298 patients who had surgery for colorectal cancer that had spread to the liver. Blood samples were collected between two and ten weeks after surgery using a personalized ctDNA test designed for each patient’s tumor. Some patients had surgery first, while others received chemotherapy before surgery. These groups were analyzed separately.
Among patients who had surgery first, those with detectable ctDNA had a much greater chance of their cancer returning and a much higher risk of dying than patients whose blood tests were negative.
Most importantly, patients with positive ctDNA who received chemotherapy after surgery lived much longer than those who did not. Four years after surgery, overall survival reached 65 percent compared with 33 percent in patients who skipped chemotherapy. Disease-free survival was also much higher.
Patients whose ctDNA tests were negative had good outcomes whether or not they received chemotherapy, suggesting that some people may safely avoid unnecessary treatment. In patients who had already received chemotherapy before surgery, ctDNA still predicted the risk of recurrence, but extra chemotherapy after surgery did not appear to improve survival.
The findings are encouraging because they suggest ctDNA testing may help doctors personalize treatment instead of giving chemotherapy to everyone. However, the researchers and independent experts caution that the results came from a Phase II study. Larger randomized clinical trials are still needed before ctDNA-guided treatment becomes routine.
The study was presented at the ESMO Gastrointestinal Cancers Congress 2026.
Overall, this research offers an exciting step toward more personalized cancer care. It has the potential to improve survival for patients who truly need chemotherapy while reducing unnecessary side effects for others. Although further studies are essential, ctDNA testing may eventually become an important tool for guiding treatment decisions after colorectal cancer surgery.
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Source: Hyogo Medical University.
