A simple blood test could be used to predict who is at risk of developing colon cancer, scientists say.
The research could lead to a test
US researchers have found genetic "red flags" which can indicate people may develop the disease.
They say the finding could lead to drugs which could reverse the genetic fault and potentially prevent cancer.
However, the test can currently only be used for research purposes, and it could be several years before a test that is efficient enough to be used for patients is developed.
Patients in the initial study will also need to be followed to see if they develop cancer after the test is positive, they said.
We hope these findings will have the ability to identify people at increased risk for colon cancer
Professor Andrew Feinberg, Johns Hopkins University:
Colon cancer is the third most common cancer in men, and the second most common cancer in women in the UK.
Each year, there are over 18,000 new cases of colorectal cancer in men, and over 16,000 cases in women.
The researchers, from Johns Hopkins University in Baltimore, Maryland, had already found that a particular genetic fault occurred in around 40% of colon cancers.
Two copies of genes are normally inherited, one from the mother and one from the father. One is turned off, leaving the other "on."
The genetic fault involves the "wrong" copy of a gene involved in the growth process being switched on or off.
This is known technically as loss of imprinting (LOI), has been linked to several types of childhood and adult cancer, and to other diseases.
The team analysed of blood samples from 172 people who had had a colonoscopy examination.
Twenty-five who had a family or personal histories of colon cancer and polyps showed LOI in their blood.
People who had a personal history of colon cancer were nearly 22 times more likely to have LOI markers.
Those with a family history were more than five times more likely to have LOI markers than those with no family history.
Those with polyps were almost three and a half times more likely to have LOI markers in the blood.
The researchers found a chemical process can incorrectly activate the maternal copy of the IGF2 gene.
They hope to find drugs which could reverse this process and potentially prevent cancer.
Professor Andrew Feinberg, of the Kimmel Cancer Center at Johns Hopkins University: "We hope these findings will have the ability to identify people at increased risk for colon cancer, follow them closely and prevent disease or at least catch it early, similar to the approach doctors use in identifying patients at risk of heart disease."
Professor Robert Steele, an expert advisor to Colon Cancer Concern (CCC), and a specialist at Ninewells Hospital, Dundee, told BBC News Online: "This is very encouraging research.
"However, it will be several years before its place in clinical practice can be properly established.
"It will take time to follow patients' progress to see how the disease develops and also to further identify people's risk of developing colon cancer."
Dr Rob Glynne-Jones, chief medical advisor to the CCC, said: "We already know from the work on the BRCA1 and BRCA2 genes in breast cancer that there are genes which identify people who are at a higher risk.
"In colorectal cancer, there's probably more scope for earlier detection and even prevention through the wider introduction of testing."
The research is published in Science.