Misconceptions & Misunderstandings About Genetic Testing For Hereditary Cancer: Don�t Test Me, Test My Family!

April 19, 2013 Swedish Blogger

As a genetic counselor with 30 years of experience, I have met with many families who have been concerned about their hereditary risks to develop cancer and other disorders. I have found that the complexity of genetics can sometimes cause misunderstandings about some critical information.

A common question that patients ask is this: I already have cancer, it makes no sense for me to have genetic testing, so why don’t you test my family instead?

As it turns out, the best strategy for most families is to for genetic testing to start with a relative who has already been diagnosed with cancer.

  1. If that person has a normal genetic test result, there is usually no need to test any other healthy family members.
  2. Because of the complicated nature of cancer genetics, accurate interpretation of a negative result usually requires an affected relative to have a positive genetic test.
  3. If a patient has a positive genetic test, the cost of testing all other family members will usually be considerably less expensive and increases the likelihood that health insurers will cover the test.

Let’s clarify this with a specific example.

Three sisters, all in their 30s, want to undergo genetic testing because their mother is a breast cancer survivor, and their maternal grandmother, and 2 maternal aunts have also been diagnosed with breast cancer. If all three sisters undergo testing, the total cost would be about $12,000 (~$4,000 per test for each sister). And, if they all have a normal (or negative result), it is still difficult to determine their breast cancer risks because we do not know if their mother does indeed carry a known breast cancer genetic marker.

If the mother first has genetic testing and has normal results, there is no need to test the daughters. These daughters would still be at some increased risk of developing breast cancer because of the family history but their breast cancer risk is likely to be lower than if they had a positive genetic test.

If the mother has a positive result, then all of her daughters should consider genetic testing. However, because the laboratory has now identified the specific genetic marker that is causing cancer in this family, the total cost of testing the sisters is ~$1500 (~$500 per test for each sister). And, if a sister has a normal result, we can confidently tell her that her risk of developing breast cancer is the same as the average woman’s risk, nor could she pass on the genetic marker to her children.

Sharing genetic test results with family members can be an emotionally and medically complicated discussion. An experienced genetic counselor can work with you and your family to make sure your family fully understands the impact and importance of genetic testing.

Of course, this strategy is not possible in all families but we try to use this approach whenever possible so patients can get the most accurate and helpful information for planning their medical care.

The Hereditary Cancer Clinic at Swedish offers genetic counseling to patients with cancer and their families. You can learn more about the Hereditary Cancer Clinic here. To learn more about genetic counseling, visit the website of the National Society of Genetic Counselors at www.nsgc.org.

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