The people in these two families have a slightly more than two out of three risk (69%) of getting colon cancer—specifically, attenuated familial adenomatous polyposis (AFAP), a form of inherited colon cancer from the adenomatous polyposis coli (APC) gene that can lead to AFAP—characterized by less than one hundred adenomatous polyps in the colon and rectum, by the age of 80 years.

The general population in the United States has a slightly less than one in twenty-four chance (about 4%).

A hereditary form of colon cancer, what is called “founder mutation” (a defect in DNA that is traceable back to a common ancestor), was found to have been brought over from England to the United States by one colonial family in the 1630s, the time of the early settling of the country.

Because family members in England do not have the increased risk from colon cancer, the researchers contend that the one couple that came over to the United States ended the English family link with the disease, but established it in the United States.

Although only a few thousand people in the United States now carry this increased risk for colon cancer, the researchers of this study contend that this genetic mutation could mean many more other people could also carry the increased chance for this hereditary form of colon cancer, only it has not been identified yet.

In fact, U.S. genetics researcher Deborah Neklason, the study’s leader states, “The fact that this mutation can be traced so far back in time suggests that it could be carried by many more families in the United States than is currently known." . [Telegraph: “How the English gave America bowel cancer”]

The study also describes thirteen more U.S. families with the same genetic defect who are likely to be related to this common colonial ancestor.

The researchers published their study (“American Founder Mutation for Attenuated Familial Adenomatous Polyposis”) in the journal Clinical Gastroenterology and Hepatology on December 6, 2007. The researchers included: Deborah W. Neklason, Jeffery Stevens, Kenneth M. Boucher, Richard A. Kerber, Nori Matsunami, Jahn Barlow, Geraldine Mineau, Mark F. Leppert, and Randall W. Burt.

The Neklason team suggests that "genetic testing should be considered for people with a family history of 10 or more colon polyps" . [CBS News: “Did The Pilgrims Carry Colon Cancer?”]

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