Genetic Counseling and Genetic Testing
What are gene mutations?
Genes are pieces of DNA. Genes help decide which traits, like eye and hair color, are passed down from parents to their children. Just as genes can affect your height and eye color, they can also affect how likely you are to develop certain cancers.
Changes in genes are called gene mutations. Genetic mutations can be passed down from parents to children. These are called “germline mutations.” These mutations affect how certain cells work and can raise your risk of cancer. About 5-20% of all cancers are thought to be caused by gene mutations that are hereditary (passed down through the family). Family history is an important part of your cancer risk. However, just because you have a family history of cancer does not mean that you have a gene mutation or that you will get cancer.
Genetic testing is one way to learn about your risk of developing certain types of cancer. The best way to start this process is to schedule a visit with a genetic counselor.
What are genetic testing and genetic counseling?
Genetic testing uses samples from your body (like a blood sample, cheek swab, or amniotic/placenta testing during pregnancy) to look for certain mutations in your genes. There are many known mutations that are linked to an increased risk of cancer. As more research is done, we will learn about even more genes that may be linked with cancer risk.
Some known genes linked to cancer are:
- BRCA1 and BRCA2: Mutations in BRCA1 or BRCA2 have been linked with an increased risk of breast and ovarian cancer, as well as pancreatic cancer, prostate cancer, and melanoma.
- P53: 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.
- MSH2, MSH6, MLH1, PMS2, EPCAM: People with a mutation in one of these genes have a syndrome called Hereditary Non-polyposis Colorectal Cancer (HNPCC), also called “Lynch Syndrome.” People with this syndrome are at a higher risk than the average person for developing prostate, stomach, colorectal, and several other cancers.
- STK11: This gene mutation causes a rare genetic syndrome called Peutz-Jeghers syndrome. This syndrome causes polyps in the stomach and intestines during the teenage years. People with this syndrome have a higher chance of certain cancers, including cancers of the stomach, esophagus, colon, and small intestine. Women with this syndrome have an increased risk of ovarian cancer.
- ATM, BRIP1, RAD51C, RAD51D, and PALB2: These genes have been linked with ovarian, breast, and pancreas cancers.
A genetic counselor is a provider who has special training in the study of genes. The counselor will:
- Explain why genetic testing may or may not be right for you.
- Ask about your family and personal history.
- Ask why you or your provider wish to have genetic testing done.
- Look into your insurance and the possible costs of testing.
- Tell you about how the sample will be collected, what it will look for, and how long it might take for results.
- Go over the results with you and what those results might mean for you and your family (positive, negative, or inconclusive).
- Discuss lifestyle changes and early detection (screening) tests if you have an increased cancer risk.
- Give advice on how to cope with your results and how to talk with family members about possible cancer risks.
Why is genetic testing important?
Genetic testing can be used in a few ways to learn more about your cancer or your risk of getting cancer. Your provider may suggest genetic testing:
- If it seems like there is a strong family history of certain cancers. If a genetic mutation is found, your provider may suggest screening tests to look for cancer earlier and/or more often than the general public. This can be done to prevent cancer or find it early.
- If you have cancer already, your provider may use genetic testing to see if it is a hereditary cancer (especially if you were diagnosed at a young age or there is a strong family history). A hereditary cancer may put you at risk for other cancers.
- If you are a family member of someone diagnosed with cancer who has a genetic mutation. You may wish to be tested to determine if you have a mutation. If you do, you can have screening tests to look for cancer and can make lifestyle changes to decrease your risk.
Who should see a genetic counselor?
Genetic counseling might be right for you if you have:
- More than 2 first-degree relatives with cancer (mother, father, sister, brother, children).
- More than 3 relatives on one side of your family (mother’s or father’s side) who have had the same cancer.
- People in your family who have multiple cancers that are linked to the same gene mutation (like breast, ovarian, pancreatic).
- A family member with more than 1 type of cancer.
- A family member diagnosed with cancer at a young age.
- Close relatives with cancer who have a type of hereditary cancer syndrome.
- A family member with rare cancer (for example, retinoblastoma).
- A family tie to certain ancestry or ethnicities, especially Jewish ancestry.
- A known genetic mutation that has been found in 1 or more family members.
Your healthcare provider should have a list of genetic counselors in your area if you would like to make an appointment. You can also find a list of certified genetic counselors at the National Society of Genetic Counselors or the National Cancer Institute.
If, after talking with a genetic counselor, you don’t feel comfortable having testing done, that is your right to make that decision.
Talk with your healthcare provider about genetic testing if you are concerned about a family history of cancer, or have had cancer yourself. To learn more about specific cancers and known gene mutations, as well as genetic syndromes, visit our section Genetics and Family History.
Resources for More Information
- Learn more about Genetic Syndromes on OncoLink.
- Find a genetic counselor in your area on the National Society of Genetic Counselors website.
- The National Institute of Health's Genetics Information page.
- Facing Our Risk of Cancer Empowered (FORCE) http://www.facingourrisk.org.
- Genetic Testing: What you need to know from the ACS.
- Genetics from Cancer.net.
American Cancer Society. (2017). Understanding genetic testing for cancer. Retrieved from https://www.cancer.org/cancer/cancer-causes/genetics/understanding-genetic-testing-for-cancer.html
American Cancer Society. (2020). What happens during genetic testing for cancer risk? Retrieved from https://www.cancer.org/cancer/cancer-causes/genetics/what-happens-during-genetic-testing-for-cancer.html
American Society of Clinical Oncology (ASCO). (2018). The genetics of cancer. Retrieved from https://www.cancer.net/navigating-cancer-care/cancer-basics/genetics/genetics-cancer
National Institutes of Health: National Cancer Institute. (2017). The genetics of cancer. Retrieved from https://www.cancer.gov/about-cancer/causes-prevention/genetics