Hereditary Cancer Testing

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What is Genetic testing? (and how does it differ from biomarker testing?)

Genetic testing for inherited cancer risk (also called hereditary cancer testing) looks at DNA from a sample of your blood or saliva to find variants (or changes in the DNA) that can make it more likely for you to get cancer in the future. 

Cancer develops because DNA variants allow cells to grow uncontrollably which can cause a tumor to develop. Most of the time DNA variants are acquired over a lifetime, due to environmental exposures, the aging process, or even by chance.  It can take years for these variants to accumulate in cells and cause a cancer. However, sometimes a person is born with a variant in their DNA – in their genetics – that increases their risk of developing cancer by making it more likely for these variations to accumulate quickly.

Genetic testing looks at the DNA that you are born with to see if you have an inherited variant that increases your risk of developing cancer. Genetic testing looks for variants that are present in every cell in the body to determine risk. Genetic testing is not cancer biomarker testing. Biomarker testing looks for variants that are present in the cancer cells to determine possible cancer treatments.  

If you have a personal or family history of certain cancers, visiting a genetic counselor to discuss the pros and cons of genetic testing for inherited cancer risk can help to determine if it's right for you. 

It can be helpful to write down your questions or notes about your family history before the appointment. After your results come back, you will have a follow-up discussion with the genetic counselor about your results and what they mean for you and your family members – like getting other cancer screenings or lowering your risk factors. You may also discuss what it means if you are currently undergoing treatment. Keeping a copy of your results from your visit can be helpful when talking with other health care providers or family members in the future.  

If you are considering genetic testing, talk with your doctor about your cancer risks and your family history of cancer. Learn more, including what questions to ask your doctor or genetic counselor from the Jackson Laboratory’s Maine Cancer Genomics Initiative at www.jax.org/patients. 

In general, only about 5 to 10% of all cancers are hereditary.

Families with hereditary cancer can identify a genetic variant which contributes to the development of certain cancers in their family.

The likelihood of a cancer being hereditary varies by tumor type. For example, about 15 to 20% of ovarian cancer is hereditary. Other cancer types, such as lung and skin cancers, have a lower likelihood of being hereditary.

If you are concerned about a pattern of cancer in your family, cancer you’ve had, or other cancer risk factors, you may want to talk to a health care provider about whether genetic counseling and testing might be a good option for you. Some risk factors may include:

  • A cancer diagnosis at a young age (usually under age 50)
  • A diagnosis of rare cancer at any age (including ovarian or pancreatic cancer)
  • Several first-degree relatives (mother, father, sisters, brothers, children) with cancer
  • Multiple relatives on one side of the family with the same or related cancers
  • A family member with more than 1 type of cancer
  • A known genetic variant in one or more family members who have already had genetic testing
  • Ashkenazi Jewish ancestry (which is linked to a higher risk of BRCA gene variants)

Before a visit, write down your family history of cancer as well as any questions you may have. Some questions you may want to ask:

  • How likely is it that I have a hereditary cancer?
  • What does the testing process look like?
  • What does it mean if I test positive?
  • If I currently or previously had cancer, will this test tell me about my risk for developing another cancer?
  • What types of things can be done to lower risk for cancer?
  • What will this testing mean for my family members, and how should I talk to them about it?
  • Will my insurance cover this type of testing?

Your health care provider can refer you to a genetic counselor in your area, or you can find a list of certified genetic counselors on the website of the National Society of Genetic Counselors.

To learn more about hereditary cancer and genetic testing visit Facing Hereditary Cancer Empowered (FORCE) or The American Cancer Society.

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