Lowering Risk for People at High Risk

If you have a family history of breast cancer, on either your mother's or father's side, you might have a higher risk for developing breast cancer during your lifetime. The most significant family history is if women in your family were diagnosed with breast cancer before the age of 50, if they had breast cancer in both breasts, and if anyone also had ovarian cancer.

But having a family history of breast cancer doesn't ALWAYS mean that your risk is increased. For example, if your grandmother was diagnosed with breast cancer at age 75, your risk of the disease is probably not increased. Your grandmother was most likely just one of the women who gets breast cancer in advanced age. Breast cancer risk increases as you get older.

Genetics

Some women with a strong family history of breast cancer have inherited a specific gene abnormality that increases their risk for the disease. The BReast CAncer 1 (BRCA1) and BReast CAncer 2 (BRCA2) gene abnormalities are the most common types that are linked to a high risk for breast cancer (as well as ovarian cancer). However, BRCA1 and BRCA2 abnormalities only account for up to 10% of all breast cancers and 7% of ovarian cancers. There are other, lesser-known genetic abnormalities in some families, with less common cancer syndromes.

Women who have an abnormal BRCA1 or BRCA2 gene have a 50–85% risk of breast cancer by the age of 70. And their lifetime risk for ovarian cancer is also increased: to 40–60% for women with BRCA1 mutations and to about 25% for women with BRCA2 mutations.

Not all inherited forms of breast cancer are due to abnormal BRCA1 or BRCA2 genes. The CHEK2 gene may play a role in the development of some breast cancers. Having an abnormal CHEK2 gene may double a woman's risk of getting breast cancer—from the average 14% lifetime risk to about 28%. Some women may have an abnormal BRCA1 or BRCA2 gene AND an abnormal CHEK2 gene. In that case the abnormal CHEK2 gene does not further increase the risk of getting breast cancer because it is part of the same cell mechanism.