Individuals with Lynch syndrome, a genetic condition that has long been known to carry dramatically increased risk of colorectal cancer and uterine cancer, now also have an increased risk of breast cancer. This is the conclusion of a study in the journal Genetics in Medicine which is published by Springer Nature. Lead author, Maegan Roberts, and a team of researchers at the company GeneDx and Columbia University in the US suggest that women who carry the particular genes responsible for Lynch Syndrome, known as MSH6 and PMS2, may benefit from more intensive breast cancer screening. Genetics in Medicine is the official journal of the American College of Medical Genetics and Genomics.
Lynch syndrome is common in the general population (estimated to affect 1 in 370 people). This hereditary condition has no specific symptoms but is identified through the presence of mutation in the so-called mismatch repair (MMR) genes. Individuals reporting a personal or family history of colorectal and uterine cancers are often tested for these genes. However, genetic tests are generally not included when breast cancer is the predominant cancer in a family.
Roberts and her colleagues reviewed the GeneDx database of more than 50,000 adult women who had undergone genetic testing between 2013 and 2016. Of these, 423 women tested positive for a variant of the four MMR genes. The researchers compiled the cancer history of these women and their family members. The breast cancer incidence in the study population was compared to cancer incidence in the general population.
In particular, the researchers found that women who possessed two variants of MMR genes called MSH6 and PMS2 had a 2-fold or 3-fold increased risk of developing breast cancer, while no breast cancer association was observed for two of the other variants. One in every four of the 423 women reported a history of breast cancer, which was first diagnosed at an average age of 50.
"Our data demonstrate that two MMR genes, MSH6 and PMS2, are associated with an increased risk for breast cancer and should be considered when ordering genetic testing for individuals who have a personal and/or family history of breast cancer," says Roberts. "Given that Lynch syndrome is not rare in the general population, this finding has the potential to impact tens of thousands of people in the US."
Reference: Roberts, M.E. et al (2017). MSH6 and PMS2 Germline Pathogenic Variants Implicated in Lynch Syndrome are Associated with Breast Cancer, Genetics in Medicine DOI: 10.1038/GIM.2017.254