Triple Negative Breast Cancer

Genetic Testing

Genetic testing is a tool that doctors can use to determine a person’s risk for certain types of cancer and/or as a guide for making treatment decisions in patients that have already been diagnosed with cancer. It is performed to look for mutations in genes. A genetic mutation is a permanent alteration in the DNA sequence of a gene within a cell. When some genes mutate, they may produce many abnormal genes or proteins that can negatively affect the cells, permitting uncontrolled, interrupted growth, which may lead to cancer.

All cancers are caused by mutations, which are classified as either acquired or hereditary.

  • Acquired mutations are genetic damage that accumulates during a person’s lifetime from a variety of factors, such as radiation, environmental exposure, smoking and diet. These are the most common mutations leading to cancer, and they can be detected by performing genetic testing on tumor tissue.
  • Hereditary mutations are passed from parent to child at conception. Also known as germline mutations, these are less common than acquired mutations. Genetic testing may be used to detect these mutations to determine future cancer risk, especially if there is a history of certain cancers in the family. However, inheriting a germline mutation doesn’t mean a person will automatically develop cancer; it only means the risk is increased. These inherited/germline mutations are typically detected by genetic testing performed on a sample of blood or saliva.

The most common hereditary mutations associated with breast cancer risk are detected in the breast cancer 1 and 2 genes (BRCA1 and BRCA2). Mutations in the BRCA1 and BRCA2 genes can increase the risk of developing breast and ovarian cancers. Proteins produced by these genes normally repair damaged DNA. When these genes are mutated, the damaged DNA is not repaired, which may lead to additional cellular alterations that may lead to cancer. Most cases of breast and ovarian cancer, however, are not caused by these hereditary/germline genetic mutations.

Researchers have discovered that triple negative breast cancer (TNBC) occurs in three quarters of women who have BRCA1 mutations and in about one-tenth of women with BRCA2 mutations. Knowing you have a specific genetic mutation may help your doctor choose the best treatment option for you, and this information may be useful to family members who can then decide to undergo genetic testing themselves. New treatment options are available for TNBC that expresses a BRCA mutation (see Treatment Options).

Who Should Get Genetic Testing?

Genetic testing may be performed before or after being diagnosed with cancer. If you have a family history of breast or gynecologic cancers or other factors, your doctor may recommend genetic testing to determine if you have hereditary mutations. Knowing this type of information can empower you to make important decisions about your health.

Breast oncology experts encourage all breast cancer patients to receive genetic testing because they may have the following characteristics associated with an increased likelihood of carrying a BRCA1 or BRCA2 mutation:

  • A family history of cancer in two or more relatives. It is important to remember that BRCA1 and BRCA2 mutations can be passed on from your mother or your father, so you should try to learn about your maternal as well as paternal family history.
  • Breast and ovarian cancer on the same side of the family.
  • A family member who was diagnosed with cancer at an early age.
  • A known genetic mutation linked to breast cancer in your family.
  • Family members who were diagnosed with ovarian cancer, sarcoma or certain other rare cancers.
  • A woman diagnosed with breast cancer under the age of 50 even if there is no family history of cancer.
  • A male family member with breast cancer.
  • Selected ancestral backgrounds are associated with BRCA mutations as well, such as Ashkenazi Jewish heritage. Several studies are also demonstrating an increased risk of BRCA mutations in African American patients, but additional research in this area is warranted.
  • Having bilateral breast cancer.
  • Having TNBC (regardless of family history), especially if diagnosed younger than the age of 60.

In most cases, genetic tests are ordered by a doctor or other health care provider. Doctors send these tests to laboratories that are regulated under the Clinical Laboratory Improvement Amendments (CLIA) program to meet standards for accuracy and reliability.

Although some direct-to-consumer genetic tests are available, they are not recommended for a person who has cancer. The sensitivity and accuracy of these tests are unknown compared to those used by doctors and designated laboratories; they typically provide raw data without offering assistance interpreting the results or providing genetic counseling; and the tests may not screen for all the possible genes and mutations for a particular cancer.

Although BRCA1 and BRCA2 are the most well-known genetic mutations in breast cancer, other mutations play a role in developing breast cancer or TNBC specifically. Mutations associated with a high risk of TNBC currently include the genes BARD1, BRCA1, BRCA2, PALB2 and RAD51D. The genes BRIP1, RAD51C and TP53 are associated with a moderate risk of TNBC. Most doctors will order a genetic testing panel looking for multiple mutations in addition to BRCA.

The Importance of Genetic Counseling

If you are interested in genetic testing, it is highly recommended that you talk to your doctor or to a genetic counselor who is trained to interpret the results and assist you in lowering your risk for developing cancer. Understanding and interpreting the results of genetic testing can be challenging.

Many different types of mutations can be identified in these genes, and some mutations will be associated with a higher risk of cancer than others. Conversely, some cases of hereditary cancer may be associated with genetic mutations that have not yet been identified, and the standard genetic testing will be negative. Consulting with a genetic counselor before testing will help you understand the role of testing in your care as well as your risks for cancer.

After testing, your counselor can use the results to determine and plan future health care, such as a schedule for screenings for you and family members, if appropriate. If a mutation is identified, your genetic counselor may discuss options to reduce your risk, including earlier or more frequent screenings, lifestyle changes or preventive treatments. Family members may be offered testing if a mutation is found.


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