The genetic epidemiology of breast cancer genes.

Genetic susceptibility to breast cancer in women is conferred by a large number of genes, of which six have so far been identified. In the context of multiple-case families, BRCA1 and BRCA2 are the most important. Mutations in these genes confer high lifetime risks of breast cancer and ovarian cancer, and more moderate risks of prostate cancer and some other cancer types. Mutations in the CHEK2 and ATM genes, by contrast, cause much more modest (2-4 fold) risks of breast cancer. Genes so far identified explain approximately 20% of the familial aggregation of breast cancer. The remaining susceptibility genes have, so far, proved illusive, suggesting that they are numerous and confer moderate risks. A variety of techniques including genome-wide association studies, use of quantitative intermediate endpoints, and resequencing of genes may be required to identify them. The identification of such genes can provide a basis for targeted prevention of breast cancer.