One in eight women, or 12 percent of the female population, will develop breast cancer in their lifetimes. Many of the factors that can affect this risk have been identified, including age, ethnicity, lifestyle, family history and genetic conditions.
Genetic counselors can evaluate a family history to determine whether there might be an increased risk for breast cancer or a risk for a hereditary form of breast cancer.
Five percent to 10 percent of breast cancers are hereditary, which means a specific gene has been passed down in a family. The most common cause of hereditary breast cancer is an inherited change, known as a mutation, in the BRCA1 or BRCA2 genes.
Normally, these genes work to prevent breast and ovarian cancer. However, if a woman has inherited a changed copy of either gene, she has a high risk of developing breast cancer. The risk might be as high as 87 percent for some families, and these cancers often occur in younger women.
Genetic testing is available to identify families with hereditary breast cancer due to BRCA mutations. By identifying people who carry these genetic changes, genetic counselors are able to discuss increased screening and preventive-surgery options with other family members who have inherited the same genetic risk factor.
Although the majority of breast cancers are not hereditary, family history alone can affect the risk for breast cancer. Being aware of your family history can be very helpful in determining your risk. Having a first- degree relative (sister, mother or daughter) who has been diagnosed increases the risk for breast cancer. Breast cancer on your father's side of the family also might affect risk.
If there is a family history of breast cancer, the general recommendation is to start screening 10 years earlier than the youngest woman's diagnosis. For example, if a woman has been diagnosed at age 45, other women in the family should start mammograms at age 35.
It is important to keep in mind that many women with breast cancer have no apparent risk factors. In fact, the vast majority of women who are diagnosed will have no family history of breast cancer. This is why it is critical for women to have an annual mammogram starting by age 40.
Discuss breast cancer screening with your physician to determine what would be most appropriate for you.