ICARE Newsletter Fall 2023

Ask the Expert

This question was addressed by Kelly Taylor, MS, LCGC, a licensed and certified genetic counselor with expertise in
research genetics and hereditary cancers at the Vanderbilt Hereditary Cancer Clinic. If you have a question you would
like addressed, please email the ICARE team at ICARE@vumc.org for consideration in future newsletters.

Q: I have Lynch Syndrome and an MLH1 mutation. I saw a blood test to detect cancer early on TikTok. Are you
familiar with this test and can you give me advice on if this is something I could have?

A: A ctDNA test is a test that looks for circulating tumor DNA in a person’s blood. If a person has cancer, as cancer cells go through their life cycle, pieces of the DNA from the cancer cells can enter a person’s blood. A ctDNA test looks for these pieces of DNA in a person’s blood. Testing can be done for different reasons. It can be done to see if a person who has already been diagnosed with a cancer to see if their cancer may have returned or may have spread. It can be done in a person who has not been diagnosed with cancer to see if they might have cancer.

This type of test is not approved by the FDA for people who have not been diagnosed with cancer. More research is needed before this type of test can be used for people who have not had cancer. The test can have false negatives – meaning the test is normal, but the person does in fact have a cancer. If the person is not having standard cancer screening, like colonoscopies, then a cancer could be missed. The test can also have false positives – meaning the test is positive, but the person does not have cancer. This could lead to follow-up tests that are not needed such as x-rays or scans that might not be covered by insurance; and to anxiety about the possibility of having cancer, even when scans are not able to find anything.

At this time, insurance is unlikely to pay for this test since it would be considered experimental, so you would most likely have to pay for this out of pocket. Even if a patient has the test and pays for it themselves, insurance may not pay for follow-up after a positive test. Regardless of what you decide, it is important that you continue to have the standard recommended screening for Lynch Syndrome (like colonoscopies).

Additional readings that may be helpful include:
1Carr DJ, Welch HG. JAMA Intern Med. 2023. Online ahead of print. PMID: 37639262;

2Connal S, Cameron JM, Sala A, Brennan PM, Palmer DS, Palmer JD, Perlow H, Baker MJ. J Transl Med. 2023;21(1):118. PMID: 36774504;

3. Ignatiadis M, Sledge GW, Jeffrey SS. Nat Rev Clin Oncol. 202;18(5):297-312. PMID: 33473219.

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