More than 70 percent of women who develop breast cancer have no known risk factors. Nevertheless, there are several risk factors that can increase a woman's chances of developing cancer. The most important risk factor is age -- the older a woman is, the greater her chance of getting breast cancer.
A woman is at increased risk for breast cancer if she is childless, or if she had her first child after age 30. Early menstruation and the consumption of alcohol (3 or more drinks a day) are also associated with an increased risk for breast cancer. The role of oral contraceptives in relation to breast cancer risk is still unclear at this time. Evidence suggests that exercise and good nutrition may help reduce a woman's risk of developing breast cancer.
Genetic Risk
With the exception of age, the greatest risk factor for breast cancer is a family history of this disease. About 20 percent of women with breast cancer have a family history of one or two relatives with the disease.
About five percent of women with breast cancer have several relatives who have had breast cancer and/or ovarian cancer. Two genes, called BRCA1 and BRCA2 have been linked to these families. When someone inherits an altered form of one of these genes (called a mutation), that person has a markedly increased risk of breast and/or ovarian cancer. This genetic mutation can be inherited from the mother's side of the family or from the father's side. In these families, the risk for a woman developing breast cancer or ovarian cancer can approach 90 percent by age 70. Men inheriting BRCA1 or BRCA2 mutations also have an increased risk of breast cancer, although breast cancer is much less common in men.
There may be other, as yet undiscovered genes that are linked to families with breast cancer. In addition, in rare families there may be syndromes that cause breast cancer. For example, in some families breast cancers and sarcoma are caused by mutations in a gene called p53.
Identification of Genetic Risk Factors for Breast Cancer
Women with a family history of breast or ovarian cancer should consider genetic counseling. (This is particularly important for those whose family members developed these cancers at an early age -- generally before menopause). Memorial Sloan-Kettering has a New York State approved laboratory that offers genetic counseling services. Our Clinical Genetics Service can discuss your options for genetic testing in a counseling session. Insurance will generally cover the costs of counseling but the decision regarding whether to submit testing charges to insurers can be discussed at the time of counseling. There are special issues of privacy of genetic information that must be considered. In some cases, research studies may cover the costs of the laboratory testing.
Screening & Prevention Options for Those at Increased Risk
For women with family histories of breast or ovarian cancer, and those with mutations of BRCA1 or BRCA2, there are an increasing number of options for early detection or prevention. These include breast self-examination, physician examination, mammography, sonography, and magnetic resonance imaging (MRI). Risk-reducing surgery is also an option. In some cases women opt to remove breast tissue or ovaries (generally after childbearing) to reduce the risk of hereditary cancers.
An emerging area of research involves use of chemoprevention agents such as tamoxifen and, possibly raloxifene (see STAR trial and announcement of initial results of this study). Our researchers are taking part in a study to determine whether women who take these drugs lower their breast cancer risk.
Women who would like to discuss their family risk factors for breast or ovarian cancer should first speak to their physicians and then can schedule a genetic counseling session by calling 212-434-5149.
