Recent large-scale genomic analyses have uncovered dozens of common genetic variants that are associated with breast cancer. Each variant, however, contributes only a tiny amount to a person's overall risk of developing the disease. A Mayo Clinic-led team of international researchers has now combined 77 of these common genetic variants into a single risk factor that can be used to improve the identification of women with an elevated risk of breast cancer. This factor, known as a polygenic risk score, was built from the genetic data of more than 67,000 women. The results of the research were published online on April 2, 2015, in the Journal of the National Cancer Institute (JNCI). A companion study has extended this finding to show that this measure of genetic variation can be combined with traditional predictors of breast cancer risk such as breast density and family history to improve personalized estimates of breast cancer risk. These latter findings appeared in JNCI last month. "This genetic risk factor adds valuable information to what we already know can affect a woman's chances of developing breast cancer," says study co-author Celine Vachon, Ph.D., an epidemiologist at the Mayo Clinic. "We are currently developing a test based on these results, and though it isn't ready for clinical use yet, I think that within the next few years we will be using this approach for better personalized screening and prevention strategies for our patients." Scientists have known for decades that genetics can play a role in breast cancer. For example, inheriting a mutation in BRCA1 or BRCA2 genes greatly increase a woman's risk of developing the disease, but these mutations are rare and account for less than five percent of all breast cancers.
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