A significant number of women with breast cancer have a family history of the disease, but only 5 to 10 percent of all breast cancer cases are actually hereditary. A woman is two to three times more likely than the general population to develop breast cancer if a first-degree relative (mother, sister, or daughter) has had the disease. If more than one close relative has had breast cancer, the risk is higher. This increased risk is even higher if the relatives developed cancer at a young age (before the onset of menopause) or in both breasts. If there are certain other types of cancer in the family, especially male breast cancer or ovarian cancer, the chance of a mutation increases.
Patients with hereditary breast cancer are predisposed to the disease because they are born with mutations in the BRCA1 or BRCA2 genes. A woman can inherit these genes from her father or mother. These genes have normal functions within cells, perhaps as caretakers that repair DNA when it is damaged. When a person is born with one abnormal copy of either of these genes, the other copy is able to make up for it and the cells function normally. However, if both copies are damaged, the cell is predisposed to become cancerous. Women with BRCA mutations may also have an increased risk of developing ovarian cancer, and males with the mutation are at increased risk of developing prostate cancer. Women without the BRCA mutation have two normal copies of the gene and are at less risk of developing the disease. In the future, other genes involved in the development of breast cancer may be identified.
Genetic Counseling
When a woman is diagnosed with breast cancer, she may be wondering if she and members of her family should be tested for the gene mutations associated with breast cancer. In most cases, the answer is no. The mutated form of the gene is responsible for only a small percentage of breast cancers.
However, she and her relatives might consider genetic counseling (and perhaps testing) if several members of the family in multiple generations developed breast cancer or other forms of cancer, if breast cancer occurred at a fairly young age, or if it occurred in both breasts. Women who are of Ashkenazi (Eastern and Central European) Jewish ancestry and also have a family history of breast or ovarian cancer should consider counseling.
Genetic counseling usually involves several sessions with a trained counselor. The counselor will explore and chart a woman's family history of disease, discuss her personal risk factors, and estimate her risk for disease. She or he will also determine whether the genes BRCA1 and BRCA2 might be a factor and will talk about the emotional aspects of testing for mutations in these genes.
Genetic testing cannot predict whether or not a woman or a family member will develop breast cancer. It can only tell her if it is more likely.
The Clinical Genetics Service at Memorial Sloan-Kettering Cancer Center offers hereditary cancer risk assessment, genetic counseling, and genetic testing by specially trained genetic counselors and physicians to people who are concerned about their personal and/or family history of cancer.
