Bowel cancer is the third most common cancer in the UK
UK scientists say they have found a marker for aggressive bowel cancers needing the most treatment.
Patients most likely to develop a more virulent strain of the disease could be pinpointed by a test which looks for a marker protein called Lamin A.
These patients should be given chemotherapy in addition to standard surgery to improve survival, the Durham University/NESCI scientists say.
Their work is published in the scientific journal PLoS ONE.
The team now aims to develop a Lamin A-based detection test for use in the health service.
Bowel cancer is the third most common cancer in the UK. Each year more than 36,000 people are diagnosed with the disease.
Almost three quarters of cases occur in people aged 65 and over. Chemotherapy is rarely used in their treatment as it could cause more harm than benefit in patients who are elderly and frail.
However, for the most aggressive cancers, chemotherapy can be a big help.
The scientists studied tissue samples from 700 bowel cancer patients and tracked their progress.
The patients who had the stem cell marker protein Lamin A present in their tissue were more likely to have an aggressive form of the disease.
The findings suggests that around one third of these patients will express the Lamin A stem cell marker and should be considered for chemotherapy.
Study co-author Professor Chris Hutchison, of Durham University and North East England Stem Cell Institute, said: "Currently the hospitals use a standard test to work out how far the cancer has progressed and then they use this to determine the treatment the patient should receive.
"However, we are potentially able to more accurately predict who would benefit from chemotherapy."
Colleague Professor Robert Wilson, consultant surgeon and bowel cancer specialist at The James Cook University Hospital, Middlesbrough, said: "Chemotherapy can be very useful but can have a number of side effects, so we only want to use it where we think there's a good chance it will help. This test will help us determine that."
Mark Matfield of the Association for International Cancer Research said: "There is a desperate need for more effective treatments for bowel cancer. The problem is identifying which cancers need which treatments. This discovery may show us the way to do that and help save a lot of lives."
Hazel Nunn of Cancer Research UK said: "The key with treating any type of cancer is being able to decide on the best treatment for an individual patient. We welcome the findings of this study, which could take us a step closer towards an era of more personalised medicine."