Is There Any Relationship between Breast Cancer and Family Genetics?

When the topic of breast cancer comes up, most women with an increased risk of breast cancer related to a family history of the same will think of three things: mutations in the BRCA1 and BRCA2 genes, early onset of menstruation (starting before age 12), and a mother and/or sister who have had this form of cancer. The link between the familial history of breast cancer and genetic mutations is controversial. The medical literature about it is inconsistent and sometimes contradictory.

Women who carry the BRCA1 or BRCA2 gene mutation have a higher risk of developing breast cancer and ovarian cancer than women without this genetic abnormality.

The most recent estimates suggest that BRCA1 mutations exist in about 2% of women with breast cancer, while BRCA2 mutations exist in about 1% of women with breast cancer. Women with a family history of breast or ovarian cancer are more likely to carry one of these mutations.

If someone in your family has had breast or ovarian cancer, you may wonder if you are at higher risk for developing one of these diseases. The short answer is that it depends on how close you were to the person diagnosed with the disease and how many close relatives were affected by it. The more closely related you were to that person—for example, if they were your mother or sister—and the more relatives who had been diagnosed with breast or ovarian cancer are all considerations when interpreting potential risk.

Breast cancer is one of the most common diseases in the world. Approximately 200,000 women are diagnosed with breast cancer annually in the United States. The chances of getting breast cancer during one's lifetime are one in nine for American women. There is a very small chance of developing hereditary breast cancer caused by a genetic mutation passed down from parents to their children. Breast cancer caused by hereditary factors is a very rare cancer affecting women. Five to ten percent of all breast cancers and 27 percent of all ovarian cancers exhibit this feature.

Breast cancer risk is not inherited. The majority of breast cancers are not inherited and are not caused by an abnormal gene. Researchers estimate that less than 5% of all breast cancers can be attributed to inherited genetic mutations.

If you have a family history of breast cancer — especially if it involves multiple generations — you may be concerned about your own risk. But don't panic: The likelihood that you will develop breast cancer is still small. Almost all women with a family history of breast cancer will never develop the disease.

Women with a family history of breast cancer should talk with their doctor about whether they need more frequent screenings or additional testing for early signs of the disease (such as mammograms). It's important to note that even if you have a close relative with breast cancer, it doesn't mean you will develop the disease yourself.

If you have concerns about your risk, talk to your doctor or genetic counselor, who can help you understand your risk based on your family history and what tests may be available to help determine whether you have a genetic mutation that could increase your risk of developing breast cancer. Mammogram screening generally begins at 40 but could begin sooner with any concerns through meeting with your physician.

Family history is only one of many risk factors, and genetics are not a major factor. If you have a family history of breast and ovarian cancer, consult a genetic counselor before having bilateral breast cancer risk assessment (BRCA) testing. If you have an increased chance of carrying a BRCA mutation, unnecessary medical surveillance can lead to anxiety and the possibility of overdiagnosis and overtreatment. Consult with your doctor before making any decisions about testing.

Genetic mutations are not the only cause of breast cancer. Most breast cancers are not a result of family genetics. In these cases, genetic testing will not be helpful.

They are responsible for only 5% to 10% of all cases. Other factors may include:

Age - The risk of breast cancer rises as you get older. Most women diagnosed with breast cancer are in their 60s or 70s. Women who have their first child after age 30 have a lower risk than those who have children before age 20. The risk increases with each pregnancy and decreases after menopause.

Early exposure to female sex hormones - Girls who start menstruating at an early age or who begin having periods before age 12 are more likely to develop breast cancer later in life than girls who start menstruating later in life or after age 12 (or than boys). Girls who start menstruating between ages 11 and 14 have a slightly increased risk of developing breast cancer before age 50 compared with those whose periods started at an older age.

Many people interested in their family's health history are worried that they might carry a genetic mutation at greater risk of developing breast cancer. Are these fears justified? The short answer is no. Only a very small percentage of women who develop breast cancer have inherited a genetic mutation. There is still much to learn when considering the connection between family genetics and breast cancer.