People are normally protected against colon cancer by inheriting two healthy copies of a gene called TGFBR1, from each parent.
But in a study involving about 200 colon cancer patients at Ohio State University in Columbus, investigators found a weak copy of TGFBR1 in about 10 percent or 24 patients.
"This gene is under-expressed in these patients and it seems to cause them to have about an 8.7 times more likely [greater likelihood of contracting colon cancer] than if you don't have this particular genetic finding," said Heather Hampel.
Experts say the lifetime risk of colon cancer is six percent, particularly in the West where the disease is common. The abnormality would increase the risk of the disease to nearly fifty percent for people found to have the susceptibility gene.
As a genetic counselor, Hampel says she would urge people with the genetic abnormality to get a colonoscopy, a procedure to look for potentially cancerous polyps, at a younger age and more often.
Hampel says the genetic finding may also explain why the disease seems to run in families.
"Once you identify a patient who has this characteristic, we would want to offer testing to all of their brothers and sisters and children to let them know whether they have inherited this characteristic and also have an increased risk for cancer," she said.
Hampel says investigators have reason to believe the gene may be responsible for a higher percentage of colon cancers, something still to be teased out by genetic researchers. Meanwhile, when a blood test based on the research is available, possibly within a few years, it would allow susceptible patients to be screened regularly to catch colon cancer early, when it is most treatable.