KEY POINTS:
A married couple who sailed to America from England around 1630 are the reason thousands of people in the United States are at higher risk of a hereditary form of colon cancer, researchers said on Wednesday.
Using a genetic fingerprint, a US team traced back a so-called founder
genetic mutation found among two large families now living in Utah and New York to the couple.
Cancer researchers at the Huntsman Cancer Institute in Utah did not name the families but said thousands of people across the country might have the mutation that spread widely as the couple's descendants branched apart over many generations.
"The fact that this mutation can be traced so far back in time suggests it could be carried by many more families in the United States than is currently known," said Deb Neklason, who led the study.
"In fact, this founder mutation might be related to many colon cancer cases in the United States."
Colorectal cancer is the third-leading cause of cancer death in the United States.
It will affect 153,000 Americans this year, says the American Cancer Society, and will kill 52,000.
Family history, smoking and diet are all linked with colorectal cancer but experts are still struggling to identify the causes that underlie most cases.
Less than 1 per cent of these cases are due to this particular genetic mutation, according to the study published in Clinical Gastroenterology and Hepatology.
The US team focused on the Utah branch of the family - about 5000 people today - 14 years ago because it had an unusually high risk of colon cancer.
Because the family was Mormon, the researchers were able to mine a wealth of genealogical information taken from detailed church records over the years that is now part of a large genetics database in Utah, she said.
While most of the records in the study related to the Utah part of the family, the researchers eventually identified the New York branch as well.
"We just know about these two branches of the family," she said.
"The significance of it going so far back is there are probably many branches of the family out there that aren't aware of the mutation."
In the study, the team identified the mutation that causes a condition called attenuated familial adenomatous polyposis, which makes people more prone to developing polyps that can cause colon cancer.
Without proper treatment, people with this mutation have a greater than 2 in 3 risk of developing colon cancer by age 80, compared with about 1 in 24 for the general population.
But early treatment can just about eliminate this risk.
"This study highlights that you need to pay attention to your family history. With intervention to remove the polyps, the risk goes to near nothing."
- Reuters