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Genetic Testing for Cancer

Genetic testing can find mutations in genes that give you a higher risk for cancer. This testing is complex. There are things that are important to think about when considering genetic testing. You may want to speak with your healthcare provider. Or you may get a referral to a genetic counselor. This will help you find out more about specific testing available to you. Your family members may be affected by test results. So you may want to think about speaking with them about genetic testing as well.

Lab testing methods

Testing methods vary from lab to lab. Here are some things to keep in mind:

  • Different lab studies have the ability to find different types of mutations. Accuracy will vary. It depends on the method of testing done.

  • Sometimes the type of tissue studied (tumor vs. blood sample, for instance) also affects the odds of finding a mutation.

  • Some families may have a mutation in a gene. But the mutation is not detectable with current technology. In these cases, genetic testing may give a false-negative result. This means that you may get a normal result when there really is a problem.

  • Many genetic tests are offered by a single lab, often the one that developed or licensed the test. 

Not all people with what appears to be an inherited cancer will have a mutation. This may be because the accuracy of testing is not 100%. The tests may not look for less common mutations. Or it can happen for other reasons.

Sometimes genetic testing is done and no mutation can be found in an affected family member that has cancer. So testing unaffected relatives for the same gene will not help clarify cancer risks.

In this case, if there is a very strong family history of cancer, the person’s relatives may still have a higher risk of developing cancer because of their family history. They may need to be tested with a full panel of mutation tests.

What the test results mean

Mutation positive: The mutation is found in the person tested

The likelihood of developing various cancers depends on the gene in which the mutation is found. In some cases, it depends on where in the gene the mutation is found. Other genes and environmental risks factors may change cancer risk. Other factors are:

  • Test results give a probability, but not a certainty, of cancer development. They don’t tell you when cancer may develop or the stage or grade of a potential tumor.

  • Test results may help you be proactive about cancer surveillance or preventive measures.

  • Some test results may not change recommendations for health management or cancer surveillance. But others may have an immediate impact.

Ask your healthcare provider whether positive test results will change your management or surveillance program. 

Mutation negative: The mutation is NOT found in the person tested

If there is a known mutation in the family, then you are not at a higher risk of developing cancer based on that known mutation. If you belong to a certain ethnic group where common mutations have been found, then relatives should think about testing for all ethnic-specific mutations, not just the one present in the family.

If there is no known mutation, a negative test result is uninformative. The family may have a mutation in the gene tested that is not detectable with current technology. Or the family may have a mutation in a different gene, since many cancer syndromes are genetically heterogeneous (caused by mutations on one of several different genes).

Variant of uncertain significance

This means that an alteration in the DNA of a gene has been found. It is not known whether the change will, in fact, affect the function of the gene or influence cancer risk. Further studies may be needed. If a major family history is present, this result does not rule out a hereditary cancer syndrome in a family.

How the testing may affect you

You may become newly worried, or relieved, after testing for mutations in cancer susceptibility genes. Relationships with family members may change. This is especially true if one person is mutation positive, while another is mutation negative. You may feel guilty if you are the only person in your family without a mutation. Or you may feel that you gave a mutation to a family member. Some relatives may deny the results or blame you for bringing the "bad news." Or they may refuse to be tested, even if that will help the testing process. Communication between family members can get better or stop altogether, depending on test results. It is important to try to look ahead at potential problems in the family tied to testing before doing it. Other things to think about are:

  • Testing is costly. It may not be covered by insurance. Check with your insurance company about coverage before having the testing done.

  • Fears that your genetic information will be held against you. You may be concerned about the risk for genetic discrimination. This means that your genetic information is held against you. Health insurers and employers are not allowed to discriminate against you based on your genes. Most states also have laws regulating the use of genetic information by health insurance companies.

  • Testing choices change. Remember that technology is advancing quickly. If you are a person for whom no testing currently exists, testing options may become available in the near future.

  • Do your homework. Take the time to explore the above issues before doing this type of testing. This will help you to fully understand what your test results mean.

Remember, genetic testing is a personal choice. It is not for everyone. Only you can decide what is right for you. Genetic counselors are trained professionals who, in addition to your healthcare provider, can help you decide if testing is the right choice for you.

Online Medical Reviewer: Levy, Adam S, MD
Online Medical Reviewer: Sather, Rita, RN
Date Last Reviewed: 6/1/2018
© 2000-2018 The StayWell Company, LLC. 800 Township Line Road, Yardley, PA 19067. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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