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Breast Cancer

Genetics of Breast Cancer

Breast cancer is the most common cancer for women, with every woman having about a 13% chance of being diagnosed in her lifetime1. Many factors, some modifiable and some beyond our control, can increase or decrease a woman’s risk of breast cancer, such as alcohol consumption, hormone therapy, and childbearing2. In about 5-10% of cases, however, there is an underlying hereditary component caused by an inherited gene mutation (change) that increases breast cancer risks. Identifying if you have a higher risk of developing cancer through genetic testing can be critical to the health of you and your family.

When Should You Be Concerned About Family History?

As 5-10% of breast cancers are associated with an inherited gene change, knowing your family history of cancer is extremely important. Having a first-degree relative (such as a parent, sibling, or child) with a history of breast cancer almost doubles an individual’s lifetime breast cancer risk. Having two first-degree relatives with breast cancer increases risk about three-fold3.

Your family history can also help determine if you qualify to undergo genetic testing. We have thousands of different genes, and some of these genes’ primary function is to protect us from developing cancer. When we inherit a mutation, or a non-working copy of that gene, from one of our parents, that genetic change increases our risk of developing cancer.

What Genes Are Associated with Hereditary Breast Cancer?

Multiple genes have been identified that play a role in breast cancer development. Two of the most common genes associated with hereditary breast cancer risks are BRCA1 and BRCA2. Changes in these genes can cause Hereditary Breast and Ovarian Cancer syndrome (HBOC). HBOC increases the risk of breast cancer as well as ovarian cancer, pancreatic cancer, melanoma, prostate cancer, and male breast cancer. Although male breast cancer is not common, having a harmful mutation in BRCA1 or BRCA2 can significantly increase this risk compared to men in the general population.

While BRCA1 and BRCA2 are the most common genes with ties to hereditary predisposition to develop breast cancer, there are multiple other genes that have also been discovered to be risk factors. Therefore, if you or your family members have only had testing for BRCA1 and BRCA2 in the past, you or your relatives may be recommended to have updated genetic testing to look for a broader panel of genes. Genetic testing can be performed with either a blood or saliva sample.

Who Should Consider Genetic Testing for Breast Cancer?

Identifying if you are at an increased risk to develop breast cancer can help you and your healthcare team make decisions about your health. For someone with a new diagnosis of breast cancer, genetic test results could impact decisions for surgery and further treatment in addition to providing information for family members. For someone with no personal history of cancer, knowing your genetic information can be used to start breast cancer screening earlier or, in some cases, make decisions to have surgery to lower the risk of developing cancer in the future.

Many people could benefit from genetic screening for hereditary breast cancer, especially the following individuals:

  • Women diagnosed with breast cancer before the age of 50
  • Women diagnosed with triple-negative breast cancer at or before the age of 60
  • Women diagnosed with breast cancer with several relatives who have been diagnosed with breast, ovarian, prostate, or pancreatic cancer
  • Women of Ashkenazi Jewish descent diagnosed with breast cancer, regardless of age
  • All men diagnosed with breast cancer, regardless of age
  • Individuals with close family members diagnosed with breast, ovarian, prostate, pancreatic, or other types of cancer
  • Individuals with a close relative who has tested positive for a genetic change known to be associated with an increased risk for breast cancer

*close relatives (parents, siblings, children, nieces/nephews, aunts/uncles, grandparents, first-cousins)

Where to Begin

If you think genetic testing for hereditary breast cancer risk may be beneficial for you or your family, talk to your healthcare provider about being referred for genetic counseling. During the appointment, a genetic counselor or other healthcare provider trained in genetics will sit down and work with you to provide a detailed overview of genetics and how it relates to the breast cancer in your family. They will discuss the benefits and limitations of genetic testing and work with you to help you make the best decision for you and your family. If genetic testing is ordered, your genetic counseling provider will discuss your results and how they impact your health as well as the health of your relatives. Your genetic counseling provider will share your results with your oncology care team to help guide any possible treatment strategies or other recommendations for changes in health management.

At Virginia Oncology Associates, we offer a range of services for patients who have cancer or may be at increased risk of developing cancer. Genetic counseling and testing are just some of the many tools we use to serve the best interest of our patients. Visit us here to learn more about scheduling an appointment with one of our genetic counseling providers.

Sources:

[1] American Cancer Society

[2] American Cancer Society

[3] American Cancer Society