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Breast Health

The role of heredity in breast cancer

Genes contain the hereditary information that is passed down from parent to child. They serve as the blueprint for many features. Everyone has two copies of a gene called BRCA1 in the cells of their body, one inherited from their mother and one from their father. In most people, both BRCA1 genes function normally. But in some individuals, one copy carries a misspelling. This change, or alteration, can occur at hundreds of different sites along the BRCA1 gene. Some of these changes make a person more at risk for developing breast or ovarian cancer, and may possibly be associated with cancers of the colon and prostate.

In a recent research study, one particular alteration in BRCA1 was found to occur more frequently in a group of Jews of Eastern European descent (Ashkenazi Jews) than among other ethnic groups in the study. Approximately 1 percent of Ashkenazi individuals was found to carry this alteration in this preliminary study.

The National Cancer Institute and the National Center for Human Genome Research will soon begin another research study of the Ashkenazi Jewish population to determine exactly how common this alteration is and how often this alteration is related to the incidence of breast cancer and ovarian cancer.

Most people, who develop breast cancer, including those in the Jewish population, have normal BRCA1 genes. In fact, only about 5-10 percent of all breast cancer cases appears to be inherited and not all of these are related to BRCA1. But, although certain to be fairly low, the exact percentage of inherited breast and ovarian cancers in the Jewish population is not known.

Women with a strong family history of breast and/or ovarian cancer who have inherited an alteration in BRCA1 have a substantial risk of developing breast and/or ovarian cancer. This often occurs at an unusually early age, for instance, before menopause. But, the cancer risks for an individual without a strong family history who is found to carry the 185delAG alteration is not known. There are other factors such as lifestyle, hormonal factors, environmental influences, and other inherited traits that affect cancer risks.

Not all women who carry the BRCA1 alteration will develop breast or ovarian cancer BUT, the alteration is not the single cause of disease, only a contributing factor. There must be other factors, yet unknown, that affect the development of cancer in addition to having an altered BRCA1 gene. Therefore, people who carry the altered gene are said to have a susceptibility to breast and ovarian cancer.