Breast cancer doesn’t discriminate. But even though it can affect any woman, those who have a family history of breast cancer are at an increased risk of developing the disease compared to the general population.
That fact can cause a lot of anxiety, especially among women who have a relative (or several) who has faced breast cancer. They may be left wondering: How will my family history of breast cancer impact my own likelihood of getting diagnosed?
Here, BCRF answers common questions about hereditary breast cancer and family history.
A person’s risk of breast cancer based on family history varies depending on several factors, such as their relationship to the affected relative(s), the number of relatives who have pre-menopausal breast cancer, and even the type of breast cancer the relative(s) has.
Doctors use these factors to determine whether you have an average, moderate, or strong risk of hereditary breast cancer. In general, breast cancer risk is highest in those who have a first-degree relative with the disease or have multiple cases of breast cancer within their family.
You may be categorized as strong risk if, for example, you have one or more first-degree (or second-degree) relative(s) with one or more of the following:
About five to 10 percent of breast cancers are hereditary. However, genetic factors may account for 25 percent of breast cancers in women under age 30.
BRCA1 and BRCA2 are the most frequently mutated genes in hereditary breast cancer. In monumental breakthroughs for the field, both were first identified by BCRF investigators: Dr. Mary-Claire King (BRCA1) and Dr. Alan Ashworth (BRCA2). Both are tumor suppressor genes, meaning they prevent cells from growing and dividing too rapidly. When mutations occur in BRCA1 and BRCA2, these genes no longer function properly and cells can grow out of control, which can lead to breast cancer.
Everyone has two copies of BRCA1 and BRCA2 genes, but the good news is that mutations in these genes aren’t common, with only 1 found in every 300 to 800 people. While anyone can have BRCA mutations, they’re more common in certain groups, including Ashkenazi Jewish people, men who get breast cancer, and those who develop breast cancer when they’re under age 30.
Mutations in BRCA1 and BRCA2 can have a dramatic effect on a person’s chances of getting breast cancer. While about 13 percent of women develop breast cancer during their lives, 55 to 72 percent of women who inherit a harmful BRCA1 variant and 45 to 69 percent of women who inherit a harmful BRCA2 variant will develop breast cancer by 70–80 years of age. BRCA1 and BRCA2 mutations are also associated with a higher risk of other cancers, including ovarian, pancreatic, and prostate cancers.
BCRF researchers and others have identified many other gene mutations associated with an increased risk of breast cancer. Examples include:
TP53: TP53 provides instructions for making a protein, p53, that regulates DNA repair and cell division. Women with a rare inherited mutation in TP53 (Li-Fraumeni syndrome) have a very high risk of breast cancer.
PALB2: Those with an inherited PALB2 mutation have an estimated 35 percent of developing breast cancer by age 70. The PALB2 gene normally codes for a protein that is part of a pathway that repairs DNA damage to the cells. When a mutation is present, it prevents the repair or destruction of abnormal genes in cells, which can cause them to grow uncontrollably and form a tumor.
PTEN: The PTEN gene encodes instructions for producing an enzyme that acts as a tumor suppressor. People who have who have inherited PTEN mutations (Cowden syndrome) have a higher lifetime risk of developing breast cancer and benign breast tumors.
CHEK2: Women with mutations in CHEK2—a gene that normally helps prevent cancer—have an approximately two-fold higher risk for breast cancer compared with women in the general population.
CDHI: Women who carry inherited CDH1 mutations have a 37 percent risk of developing invasive lobular carcinoma, a form of breast cancer that originates in the milk-producing glands in the breast and represents 10 to 15 percent of all invasive breast cancers. CDH1 provides instructions for making epithelial cadherin, which acts as a tumor suppressor protein.
Other genes associated with a higher risk of breast cancer include STK11; NF1; ATM; RAD51C, RAD151D, BARD1; and EPCAM, MSH2, MLH1, MSH6, and PMS2. And researchers are also investigating other “variants of unknown significance” that may impact risk.
Yes. For instance, BRCA1 mutations are most common among Ashkenazi Jewish women (8.3 percent), followed by Hispanic women (3.5 percent), non-Hispanic white women (2.2 percent), Black women (1.3 percent), and Asian women (0.5 percent).
Learn more about how BCRF investigators are advancing our understanding of the role race and ethnicity play in inherited risk factors and hereditary breast cancer.
Not necessarily, since most women who have a family history of the disease don’t have an inherited gene mutation that significantly affects their risk. At this time, there are no official guidelines regarding which women (and men) should consider genetic counseling and testing. Some expert groups have issued their own guidelines, but not all doctors agree on them.
But in general, counseling and testing is more likely to be helpful for:
If you’re concerned about your risk of hereditary breast cancer, the first thing to do is talk to your doctor. He or she may calculate your risk using several risk assessment tools, such as the Tyrer-Cuzick model, developed by BCRF investigator Dr. Jack Cuzick. While these tools aren’t 100 percent accurate, they do give your doctor a better idea of whether you should be referred to a genetic counselor, who can help you decide if genetic testing is right for you.
The CDC states that people with a family history of breast cancer should not rely on a direct-to-consumer genetic test to assess their risk of the disease. Only one such test is approved by the FDA: the Personal Genome Service Genetic Health Risk (GHR) Report for BRCA1/BRCA2 (Selected Variants), which checks for three specific BRCA1/BRCA2 breast cancer gene mutations that are most common in Ashkenazi Jewish people.
However, there are more than 1,000 known BRCA mutations, and only a small number of Americans have the three detected by this test. And even if you are of Ashkenazi Jewish descent, the FDA warns that the test shouldn’t be used as a substitute for seeing your doctor for cancer screenings or counseling on genetic and lifestyle factors.
Other at-home genetic tests for breast cancer may check for more common BRCA mutations as well as mutations in some of the other genes mentioned above. But none of these tests check for all of them, and there’s also no guarantee the tests work since they haven’t gone through the FDA’s strict approval process. Keep in mind that there are also privacy and legal concerns with at-home genetic tests, since some testing companies share your data, even without explicit consent.
Understanding the role that heredity and ethnicity plays in breast cancer risk is an important area of focus for BCRF research. Keep reading to explore BCRF-supported investigators and projects here.
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