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Does breast cancer run in your family?

Learning that a close family member has breast cancer can leave you understandably distressed. In addition to being concerned about your loved one's health, you might also be wondering how the diagnosis will affect your own risk for breast cancer.

While it's true that a family history of breast cancer can raise your risk, it doesn't mean that you will necessarily develop the disease.

But you will want to share the details of your family history with your doctor. They can help you determine if your risk is high enough to warrant taking steps such as getting extra screenings or genetic testing.

How family history can affect your risk

For family history to raise your breast cancer risk, one of your parents, siblings or children needs to have had breast cancer.

But even then, how much it affects your risk may vary. It depends on factors such as the number of relatives affected and their ages when diagnosed.

According to the American Cancer Society (ACS), your family history may have a significant effect on your risk in these ways:

  • Having a first-degree relative (mother, sister or daughter) with breast cancer nearly doubles a woman's risk.
  • Having two first-degree relatives increases her risk about threefold.
  • Women with a father or brother who has had breast cancer also have a higher risk of the disease.

Overall, about 15% of women with breast cancer also have a family member with the disease.

A family history of breast cancer can increase your risk for a number of reasons. For one, it may point to shared lifestyle traits that may increase risk, such as not exercising or being overweight.

A family history is also a signal that you may have inherited a genetic predisposition toward breast cancer. The genes most often linked to breast cancer are called BRCA1 and BRCA2.

Around 69% of women who inherit a harmful BRCA2 mutation and about 72% of women who inherit a harmful BRCA1 mutation will develop breast cancer by age 80, according to the National Cancer Institute. (By contrast, about 12% of women overall will develop breast cancer sometime during their lives.)

That makes women with certain inherited mutations much more likely to develop breast cancer. Gene mutations also put women at higher risk for developing breast cancer at a young age.

Genetic testing can help identify BRCA1 and BRCA2 mutations. But such tests aren't appropriate for every women who has a family history of breast cancer.

Whether to have genetic testing done is a personal decision involving many factors. But if you have a strong family history of breast cancer, you may be a candidate. Women will want to weigh the risks and benefits and speak with a genetic counselor.

Lowering your risk

While your family history and your genes are beyond your control, there are steps you can take to help protect your health. For example:

Extra screening. Your doctor may suggest that you start breast cancer screening earlier than is recommended for women at average risk. You may also want to consider screening with breast MRI or ultrasound in addition to mammography.

Medicines. Drugs such as tamoxifen and raloxifene can reduce breast cancer risk, studies show. Women and their doctors should discuss the risks and benefits of preventive medicines, which may have serious side effects.

Surgery. Some women at very high risk choose preventive surgery to remove both breasts before cancer develops. Before making such a decision, you'll want to carefully consider and discuss your options with your healthcare team.

Talk to your family

Breast cancer isn't the only disease that has a family connection. Heart disease, diabetes and other forms of cancer can also run in families. To help people keep track of their family history, the Office of the Surgeon General and other government agencies have launched My Family Health Portrait.

Reviewed 1/8/2021

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