Breast Cancer and Family History

Single nucleotide polymorphisms (SNPs) and breast cancer risk

In Breast Cancer Risks, Spotlight by Karina Cox

For any woman, having a significant family history of breast cancer is the largest single risk factor for developing the disease in the future. Breast cancer can be inherited as a mutation in either of the high-risk BRCA 1/ 2 genes or the dozen or so intermediate risk genes such as ATM, CHEK2 and PALB2. The third type of inherited breast cancer comes in the form of single-nucleotide polymorphisms (SNPs). These SNPs are much more common than the rare BRCA1/2 mutations and individually most carry a minimal added risk. However, in combination the risk can be magnified and to date, over 100 SNPs have been identified. It has also been shown that SNPs contribute to the development of breast cancer in women without a family history.

In January of this year (2018), the PROCAS study (Predicting Risk of Cancer at Screening) reported their findings. The study looked at a panel of 18 SNPs together with classical risk factors for breast cancer (such as body mass index, menopausal status etc using the Tyrer-Cuzick risk model) and breast density on mammograms. They found that the 18 SNPs added important information to traditional risk assessment based on the Tyrer-Cuzick model and breast density. The hope is that by using this information, in the near future women can be stratified into appropriate groups for targeted screening and prevention. That means that some women will need more intensive screening but for those at low risk, it is conceivable that they can safely have longer intervals between their regular mammograms.