Liquid biopsies are highly specific but not as sensitive as tissue biopsies. That means, if a biomarker appears in a liquid biopsy, the physician is pretty confident the patient has that biomarker. However, if something doesn’t show up on a liquid biopsy, it doesn’t mean it’s not there. Kind of like if you looked in your closet for a shirt and saw it, you would know it is there. But if you didn’t see it, it doesn’t mean it’s not in the closet. It could have been hidden in the back or fallen on the floor.
There are a few situations that make liquid biopsies less likely to pick up results. Liquid biopsies work by looking at DNA that has been shed into the bloodstream by cancer cells. If a patient is responding well to treatment or if there is not a lot of disease in the body, there is less circulating tumor DNA, which might mean the liquid biopsy misses something.
In general, liquid biopsies are very accurate at finding point mutations like mutations in EGFR. They are slightly less accurate when finding more complex alterations such as gene fusions lor extra copies of a gene (referred to as amplification). Liquid biopsies are not able to detect histology changes like when some patients’ lung cancers change from non-small cell to small cell after treatment. However, tests are improving rapidly.
Liquid biopsies do not diagnose lung cancer, but instead may provide more information important in treatment decision-making. Liquid biopsy results come back usually in a week or less, making it an important test that can provide valuable information about treatment options.
Watch this video to learn about the different types of biomarker tests.