Clinical implications of the breast cancer susceptibility genes BRCA1 and BRCA2.

Genetic testing for BRCA1 and BRCA2 mutations has become an important part of the practice of medical oncology and clinical genetics over the past decade. Increasing numbers of women are requesting a genetic test so that they may better understand their personal risks of breast and ovarian cancer, and so that they may take appropriate measures to reduce the risk. Several of the risk factors can be modified, including breastfeeding and the use of oral contraceptives. A significant number of women opt for preventive mastectomy or oophorectomy, which will dramatically reduce the risks of breast and ovarian cancer. Chemoprevention with tamoxifen is still uncommon, largely due to women's fears of the side effects of the drug. A number of studies have shown that magnetic resonance imaging is superior to conventional mammography in terms of the early detection of breast cancer in the high-risk population. This article explores what is known about assessing genetic risk and the evidence supporting a range of preventive strategies.