Genetic Testing for Familial Breast Cancer
What is Familial Breast Cancer?
Family history is a very important part of breast cancer risk. About 5-10% of breast cancer cases are hereditary. Hereditary cancer happens when changes or mutations in genes are passed down from your parents. However, just because there seems to be a family history of cancer does not mean you will get cancer. Testing for genetic mutations is one way to get an idea of your risk of developing cancer.
What are the genetic mutations linked to breast cancer?
Mutations of genes are like spelling errors in the genetic code of a gene. Those who have a gene mutation may be at higher than average risk for developing certain cancers. A genetic mutation that increases the risk of breast cancer is present in some families.
BRCA 1& 2
BRCA1 and BRCA2 are the most common genetic mutations that cause breast cancer. These are short for “breast cancer susceptibility gene 1” and “breast cancer susceptibility gene 2.” The BRCA1 and BRCA2 genes are found in every person.
The BRCA1 and BRCA2 genes are responsible for the repair of certain types of DNA errors that may happen each time a human cell makes a copy of itself. If the gene does not have a mutation, the BRCA1 and BRCA2 genes help ensure the stability of a cell's genetic material, or DNA, and help stop uncontrolled cell growth.
Mutations of BRCA1 and BRCA2 have been linked to an increased risk for multiple types of cancer, most notably breast and ovarian cancer. Having an inherited mutation in BRCA1 or BRCA2 does not mean a person is guaranteed to develop cancer, but the chances are much higher than for someone who does not have a BRCA1 or BRCA2 mutation. People who inherit a harmful mutation in BRCA1 or BRCA2 have a lifetime risk of developing breast cancer of 50-80%, compared to 13% for an average person without the mutation.
Mutations in BRCA1 or BRCA2 may also increase the risk of pancreatic cancer and melanoma in both women and men. Men also have a higher chance to develop an earlier onset of prostate cancer or male breast cancer if a BRCA2 gene mutation is present.
Other Genes Linked to Breast Cancer
While BRCA1 and BRCA2 are by far the most common gene mutations linked to breast cancer, other gene mutations have been found to play a role in increasing risk. Most of these gene mutations do not increase the risk of breast cancer as much as the BRCA genes.
- ATM: Thought to cause a 20-60% increased risk of breast cancer. One mutated copy of this gene from either of your parents has been linked to a high rate of breast cancer in some families.
- TP53: Thought to cause an 85% increased risk of breast cancer by age 60. Mutations of this gene can cause Li-Fraumeni syndrome. This syndrome increases your risk of breast cancer, as well as some other cancers such as leukemia, brain tumors, and sarcomas.
- CHEK2: Thought to cause a 20-44% increased risk of breast cancer.
- PTEN: Thought to cause a 20-50% increased risk of breast cancer in a lifetime. Mutations in this gene can cause Cowden syndrome. This syndrome can put you at risk for both cancerous and noncancerous (benign) tumors in the breasts.
- CDH1: Thought to cause a 60% increased risk of lobular breast cancer. Mutations in this gene can cause hereditary diffuse gastric cancer (HDGC). People with this syndrome can develop a rare type of stomach cancer and have a higher risk of developing lobular breast cancer.
- STK11: Thought to cause a 32% increased risk of breast cancer by age 60. Mutations of this gene can cause Peutz-Jeghers syndrome. This syndrome increases your risk of many types of cancer, including breast cancer.
- PALB2: Thought to cause a 14% increased risk of breast cancer by age 50 and 35% by age 70.
People can inherit these mutations from their parents, or mutations can happen during a person’s lifetime.
Who should have genetic testing?
In a family with a history of breast and/or ovarian cancer, the first step may be to test a family member who has had breast or ovarian cancer. If that person is found to have a harmful genetic mutation, then other family members can be tested to see if they also have the same mutation.
If the family member who has had cancer is not available for testing, a person may still be able to be tested for the most common BRCA1 & 2 mutations. The first step is to meet with a genetic counselor who will discuss what having genetic testing can mean for you. The genetic counselor will go over the risks and benefits of testing and how results will affect cancer screening and prevention recommendations for you.
You should consider genetic testing if you or a family member has had:
- Breast cancer at age 50 or younger.
- Triple-negative breast cancer at age 60 or younger.
- Ovarian or fallopian tube cancer at any age.
- More than one breast cancer diagnosis.
- Male breast cancer.
- Breast, ovarian, or pancreatic cancer and are of Ashkenazi Jewish ancestry.
- A known mutation in a cancer risk gene.
- Breast, ovarian, pancreatic, or high-grade prostate cancer diagnosed in multiple. individuals on the same side of the family.
Genetic Testing in Men
Young men are sometimes interested in having genetic testing done at later ages, since there is no screening that starts for men until later. However, some young men are interested in genetic testing to use in their decision to choose whether to have children or not. Men who have a BRCA1 or BRCA2 gene mutation are 15-25% more likely to develop prostate cancer, and often earlier in life than men who do not have a mutation. Men with this mutation are also up to 10% more likely to develop breast cancer at some point in their life. Men with known mutations should talk with their provider about preventive care. In general, men with these mutations should have:
- Breast exams by their provider every year, starting at age 35.
- Prostate exam and PSA (prostate-specific antigen) blood test every year, starting at age 40 or 45.
The decision to have genetic testing is very personal. You should talk to a genetic counselor who is specially trained to counsel patients regarding the risks and benefits of genetic testing. If you have been diagnosed with breast cancer, talk with your provider about having genetic testing done. If a family member has been diagnosed with cancer and has a known genetic mutation, talk with your own provider to see if genetic testing is right for you.
Resources for further reading
The Basser Center for BRCA: provides education & support for individuals and families with BRCA1 and BRCA2 mutations.
Facing our Risk of Cancer Empowered: FORCE provides support, education and awareness to help those facing hereditary breast and ovarian cancer.
Sharsheret: is a national not-for-profit organization supporting Jewish women and families facing breast cancer and ovarian cancer at every stage – before, during, and after diagnosis
Antoniou, A.C., Casadei, S., Heikkinen, T., Barrowdale, D., Pylkas, K., Roberts, J. et al. (2014). Breast Cancer Risk in Families with Mutations in PALB2. N Engl J Med., 371(6), 497-506. DOI 10.1056/NEJMoa1400382
Basser Center for BRCA at Penn Medicine. (n.d.). Managing Cancer Risk. Retrieved November 11, 2020, from https://www.basser.org/patients-families/managing-cancer-risk
Lim, W., Olschwang, S., Keller, J.J., Westerman, A.M., Menko, F.H., Boardman, L.A., et al. (2004). Relative Frequency and Morphology of Cancers in STK11 Mutation Carriers. Gastroenterology (126), 1788-1794. Retrieved from https://www.gastrojournal.org/article/S0016-5085(04)00380-4/pdf
Mirandola, S., Pellini, F., Granuzzo, E., Lorenzi, M., Accordini, B., Ulgelmo, M., et al. (2019). Multidisciplinary management of CDH1 germinal mutation and prophylactic management hereditary lobular breast cancer: A case report. Int J Surg Case Rep., (58), 92-95. DOI10.1016/j.ijscr.2019.03.053
Schon, K. & Tischkowitz, M. (2017). Clinical implications of germline mutations in breast cancer: TP53. Breast Cancer Res. Treat, 167(2), 417-423. DOI 10.1007/s10549-017-4531-y.
University of California, San Francisco. (n.d.). ATM Gene. Retrieves November 10, 2020, from https://brca.ucsf.edu/atm-gene.
Zhang, H., Liang, F., Jia, Z., Song, S., & Jiang, Z. (2013). PTEN mutation, methylation and expression in breast cancer patients. Oncol Lett., 6(1), 161-168. DOI 10.3892/ol.2013.1331.