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BRCA1/2 Mutations May Not Predispose to Colon Cancer; At-Risk Should Still Be Tested

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Two teams of researchers have independently offered the latest round of data purporting that BRCA1 and BRCA2 mutations do not predispose an individual to colorectal cancer.

Mutations in these genes have been associated with an increased risk of breast and ovarian cancer, but it has been unclear whether they also increase the risk of colorectal cancer.

Despite this uncertainty, current guidelines in the United States recommend that “all BRCA1/2 mutation carriers be informed that they may be at an increased risk for colorectal cancer,” according to Tomas Kirchhoff and Kenneth Offit, researchers at the Memorial Sloan-Kettering Cancer Center.

To arrive at their results, the researchers compared the incidence of BRCA1/2 mutations in 586 Ashkenazi Jewish patients with colorectal cancer in 5,012 patients without a known history of colorectal cancer. The team “found no association between the presence of a BRCA mutation and risk of colorectal cancer,” they wrote in a statement last week.

Separately, a team from the University of Michigan, Ann Arbor, performed genetic testing on 1,422 patients with colorectal cancer and 1,566 controls in Israel. They “also found no association between the presence of a BRCA mutation and the risk of colorectal cancer,” the authors, Bethany Niell and Stephen Gruber, wrote in the statement.

Specifically, the researchers found that family history of breast cancer in a female relative was “not associated with an increased risk of colorectal cancer, even after adjusting for the presence of a BRCA founder mutation.” The team concluded that “Ashkenazi BRCA founder mutations do not confer a strongly elevated risk of colorectal cancer. Similarly,” they wrote, “a family history of breast cancer does not appear to be a strong risk factor for colorectal cancer in this population.”

Both teams’ research appears in the Jan. 7 issue of the Journal of the National Cancer Institute.

In an accompanying editorial, Judy Garber and Sapna Syngal, of the Dana-Farber Cancer Institute and Brigham and Women’s Hospital, in Boston, said that although the studies “were certainly well done,” they question whether their results “are … the final words on the subject.” They said that this and other current studies show “that it will be a small increase at most, or limited to a particular subset of mutation carriers,” they said in the statement.

“Intensified targeted colorectal cancer screening and prevention should be directed only to the subset of BRCA mutation carriers who have remarkable personal or family colorectal cancer history or other risk factors,” they said in the study.

— KL

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