Breast cancer, like other cancers, develops when changes occur in genes in breast cells. In that sense, all breast cancer has a genetic element. But, “genetic” does not mean inherited. Only an estimated 5% to 10% of breast cancer cases result from an inherited genetic predisposition to the disease. In other words, more than 90% of all breast cancer cases result from factors that are not inherited and, in many cases, are unknown.

So far, researchers have found two genes linked with breast cancer-labeled BRCA1 and BRCA2-that everyone inherits in pairs: one from our mother and one from our father. When they function normally, they are supposed to stop the growth of cancerous cells in the breast. When both genes in a pair are damaged, they don’t work properly and cancer may develop. People who inherit a damaged BRCA1 or BRCA2 gene from one parent are at greater risk of developing breast cancer than people who inherit two normal genes.

Studies can estimate risk among large numbers of people who have an inherited mutation, but not the risk for an individual woman. Women with any BRCA mutation have about a 33% to 50% risk of developing cancer by age 50, and a 56% to 87% risk by age 70. Most of the research focuses on women with a strong family history of breast or ovarian cancer (several female relatives on one side who have breast and/or ovarian cancer before age 40, cancer in both breasts, and/or cases of male breast cancer).

By being able to identify these genes through particular markers associated with the gene, doctors will know which individuals are more susceptible to cancer and therefore can follow the proper procedure. The earlier the doctor can diagnose the cancer, the more effective the treatment will be.
Scientists warn however that, although they have discovered one of the genes associated with breast cancer, there is still no cure available. They have successfully identified the gene, but presently there is no way to “repair” the gene. The recent isolation of the gene BRCA-1 has prompted investigators to identify other genes that may contribute to breast cancer, ovarian cancer and the breast-ovarian cancer syndrome.