The genetics of breast cancer

Breast cancer is the commonest cancer affecting women. A family history of breast cancer increases a woman's lifetime risk of developing the disease. Most of the genetic risk is due to low-risk and moderate-risk susceptibility alleles rather than high-penetrance genes such as BRCA1 and BRCA2. Mutations in these two tumour suppressor genes only account for about 2% of all breast cancers. Female carriers of BRCA gene mutations have a high lifetime risk of developing breast and ovarian cancer and male carriers have an increased risk of prostate and breast cancer.Women with a significant family history of breast cancer should be referred to their local cancer genetics service for a formal cancer genetics risk assessment, discussion of risk management options such as surveillance and risk-reducing surgery and consideration of genetic testing. If a BRCA gene mutation is identified in a family, predictive testing can be offered to unaffected family members to clarify risks and help with risk management decisions.In the future, BRCA mutation carriers are likely to be offered different surgical management and/or first-line chemotherapeutic agents as treatment for cancer and one day chemoprevention agents may also be available.