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Genetic testing can be an important tool in helping patients learn about their inherited cancer risk, but the results are not always as clear as patients might expect.

Just as traits such as hair color and eye color can be passed down from parents to their children, so too can the risk for developing certain types of cancer. Scientists know that certain inherited gene mutations — small changes in a person’s DNA — can increase a person’s risk for developing diseases such as breast cancer, ovarian cancer, and colon cancer. Genetic testing examines a person’s DNA to determine if such mutations are present, helping patients better understand their cancer risk and, in some cases, allowing them to take charge of their health before receiving a devastating diagnosis.

Understanding the Basics of Genetic Testing

Only five to 10 percent of all cancers are believed to be tied to an inherited gene mutation.¹ Genetic testing can help determine whether an individual has inherited a specific gene mutation (or mutations) that put him or her at higher risk for developing certain cancers. Most genetic tests require a small blood sample from the patient, but some tests can be performed using urine, saliva, or a cheek swab. The sample is sent to a special laboratory and results are usually provided to the patient’s doctor or genetic counselor within several weeks.²

Genetic testing can return one or a combination of the following results:

• Positive: The laboratory identified a genetic mutation that is associated with an inherited cancer risk.²
• Negative: The laboratory did not find the specific genetic mutation (or mutations) that the test was designed to detect.²
• Inconclusive: The laboratory was not able to determine whether a specific genetic mutation (or mutations) was present in the sample provided.²
• Variance of Uncertain Significance: The laboratory identified a genetic mutation that has not been previously associated with cancer.²

No test can provide exact answers about a person’s inherited cancer risk. Genetic testing can tell you whether a specific genetic mutation is present in your DNA, but it cannot tell you for certain that you will develop the disease associated with that mutation later in life.³

Knowing Your Cancer Risk: Is Genetic Testing Right for You?

Doctors often only recommend genetic testing for patients whose families have a history of certain cancers or patterns of cancer. According to the American Cancer Society, people who meet the following criteria might consider genetic testing:

• Cancer diagnoses in multiple first-degree relatives, including parents, siblings, or children¹
• Numerous relatives on one side of the family who have been diagnosed with the same cancer¹
• Family history of cancers linked to a single gene mutation, such as breast cancer, ovarian cancer, or pancreatic cancer¹
• Family member(s) who has been diagnosed with more than one type of cancer¹
• Family member(s) who has been diagnosed with cancer at a younger age than typically seen for that cancer, such as colon cancer¹
• Close relatives who have been diagnosed with cancers linked to rare hereditary cancer syndromes, such as Hereditary Breast & Ovarian Cancer Syndrome (HBOC), Cowden Syndrome, or Lynch Syndrome¹
• Family member(s) who has been diagnosed with a rare cancer, such as breast cancer in a male¹
• People of certain ethnicities (e.g., Jewish ancestry is linked to ovarian cancer and breast cancer)¹

Genetic testing should be ordered by a doctor, genetic counselor, or other trained health care professional. This helps ensure that the test is performed accurately and the results are interpreted by a qualified professional. Some companies now offer at-home genetic testing, but these tests typically only look for common gene mutations and do not provide any real insight into a person’s true inherited cancer risk.²

Interpreting the Results of Your Genetic Testing

If you learn that you have a genetic mutation that increases your risk for developing certain cancers, there still might be steps you can take to help lower your risk. Speak with your doctor to learn if the following measures might be helpful:

• Making healthy lifestyle changes, such as exercising regularly, quitting smoking, or eliminating alcohol consumption⁴
• Taking medications known to help reduce the risk for developing certain cancers⁴
• Having surgery to remove an organ or gland to help prevent cancer from forming⁴
• Undergoing more health screenings to help increase the chance that cancer is detected early⁴

Genetic testing is a helpful tool in understanding your inherited cancer risk, but the results are not always as clear as you might hope. If you are interested in pursuing genetic testing, speak with a trusted health care provider to assess the benefits and risks as they apply to your unique situation.  

Additional Reads You May Enjoy:

Inexpensive Tests Spur Family Members to Assess Cancer Risks

Liquid Biopsy Advances: Capturing Metastatic Cancer Cells

Faces & Voices of Cancer—In Depth: Alice-Anne Birch

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References

¹ Understanding Genetic Testing for Cancer. (2016, May 23). Retrieved August 15, 2020, from https://www.cancer.org/cancer/cancer-causes/genetics/understanding-genetic-testing-for-cancer.html 

² Genetic Testing Fact Sheet. (2019, March 15). Retrieved August 15, 2020, from https://www.cancer.gov/about-cancer/causes-prevention/genetics/genetic-testing-fact-sheet 

³ Should I Get Genetic Testing for Cancer Risk? (2016, May 23). Retrieved August 15, 2020, from https://www.cancer.org/cancer/cancer-causes/genetics/should-i-get-genetic-testing-for-cancer-risk.html 

⁴ What Happens During Genetic Testing for Cancer Risk? (2016, April 23). Retrieved August 15, 2020, from https://www.cancer.org/cancer/cancer-causes/genetics/what-happens-during-genetic-testing-for-cancer.html