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What does a liquid biopsy look for?
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A liquid biopsy is a test done on a body fluid, almost always a blood sample, instead of on a piece of tissue. What it looks for is whatever is circulating in that fluid: whole cells, and also DNA and RNA, the molecules that carry the information written inside those cells. It's like scooping water out of a river far downstream and checking it to learn what is happening upstream, without having to walk all the way up there.
Since all it takes is another sample of fluid, the test can be repeated as often as you want, with no need to cut out fresh tissue each time. The price of doing it this way is that when a tumor sheds only tiny amounts into circulation, that signal gets lost among everything else: the test's sensitivity, meaning its ability to detect what really is there, falls short, and the result can miss it.
In brief
A liquid biopsy analyzes a sample of blood or another body fluid to look for cells, DNA, RNA, or other material it contains.
This approach can allow the sample to be collected repeatedly, without having to remove a new piece of tissue each time.
When very little tumor-derived material is circulating, sensitivity may be limited, and the test may miss that signal.
Sources (3)
- National Cancer InstituteDefinition of liquid biopsy
- National Cancer InstituteMaking Liquid Biopsies More SensitivePublished
- British Journal of CancerGenomic approaches to cancer and minimal residual disease detection using circulating tumor DNAPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
Updated