Genetic Testing for Breast Cancer

While BRCA1 and BRCA2 gene mutations may increase your odds of developing breast cancer, your odds of having either mutation are pretty small. An estimated 0.25% of the general population carries a mutated BRCA gene, or about one out of every 400 people.

For some people, though, the chances of having a BRCA gene mutation are much higher. Genes are inherited, which is why knowing your family history is important when determining breast cancer risks. If one of your parents has a BRCA mutation, you have a 50% chance of inheriting the mutated gene.

Odds can also vary depending on a person’s ethnicity. For example, people of Ashkenazi Jewish descent have a 2.5% chance of inheriting a BRCA mutation, or about 10 times the rate of the general population.

Because the overall odds are so low, most experts recommend that only people with a heightened risk get tested for BRCA mutations. Likewise, insurance companies often only cover genetic counseling and testing for individuals who are at high risk. A person could be considered at high risk for BRCA mutations if they have a family history of:

• Breast cancer diagnosed before age 50.
• Male breast cancer at any age.
• Multiple relatives on the same side of the family with breast cancer, particularly if they are first-degree relatives (mother, sister, daughter).
• Multiple breast cancers in the same woman, meaning breast cancer developing in both breasts over time or at the same time.
• Both breast and ovarian cancer in the same woman.
• A history of ovarian cancer in the woman’s family, especially if a first-degree relative.
• Ashkenazi Jewish heritage.
• A significant history on the same family side (mother or father’s side) of men diagnosed young with prostate cancer, ovarian cancer, melanoma, or pancreatic cancer. (These can be signs of a BRCA2 gene mutation present in the family.)

There are also other gene mutations besides BRCA that could increase the risk of breast cancer. The most prominent of these is PALB2. As with BRCA1 and BRCA2, testing for other genetic mutations is recommended only if you are at high risk for that particular gene.

How To Get BRCA Genetic Testing

Genetic counseling is recommended for those who are interested in being tested for breast cancer gene mutations. You can talk to a doctor about getting a referral to a genetic counselor, who can help determine whether genetic testing would make sense based on family history and risk factors. Since many genetic tests only look for one specific gene mutation, the counselor can often help determine which mutations to test for.

The genetic test itself simply involves taking a small sample of blood or saliva, which is sent to a lab for analysis. Results can take several weeks or months.

Genetic testing results are not always clear-cut:

• A test result can be positive, meaning that the patient does carry the gene mutation.
• A negative test result indicates that they do not have that particular known gene mutation. It does not, however, rule out the possibility of having mutations in other genes. It also does not rule out the possibility of developing breast cancer. Most breast cancer cases are not hereditary, so everyone should still have an early detection plan.
• Genetic test results can also be uncertain or ambiguous. An ambiguous test result means that a mutation has been found on the gene, but it is not yet known whether that particular mutation has any effect on the chances of developing breast cancer.
• Someone is either negative or positive. Over time, a person cannot go from being negative to being positive or vice versa for the specific gene mutations they were tested for.

After receiving genetic test results, a patient should meet again with a genetic counselor to clarify what the results mean. Whether the results are positive, negative, or ambiguous can impact many life decisions, and a counselor can help navigate those decisions.

Genetic testing can be scary. The results also can impact other family members such as siblings and offspring; when someone tests positive for a gene mutation, their siblings and offspring will have a 50% risk of also testing positive. Having a discussion with a genetics counselor first is encouraged so a discussion about the potential scenarios can take place.

For a woman who tests positive for BRCA1 or BRCA2 gene mutation, bilateral mastectomies are usually recommended particularly if she has just been diagnosed with breast cancer.

Related reading:

• Other Breast Cancer Genes
• BRCA: The Breast Cancer Gene
• What To Do If You’ve Tested Positive