As previously stated, a liquid biopsy can be defined as a minimally invasive method to detect certain molecular biomarkers in blood, cerebrospinal fluid, or urine. Liquid biopsy typically analyzes circulating cancer cells or traces of a cancer's RNA or DNA present in a blood sample. Liquid biopsy assays have the ability to identify unique cancer mutations in the form of microscopic fragments of DNA or RNA in a patient's blood. Tumor-related circulating-free DNA or RNA is released by tumor cells and circulates in the blood of cancer patients.
The main molecular biomarkers detected in blood by a liquid biopsy assay are:
- Circulating tumor cells (CTCs)
- Circulating tumor DNA (ctDNA)
- Exosomes
This course will describe liquid biopsy assays that involve each of these biomarkers. The graphic on the right illustrates the tumor biomarkers circulating in the bloodstream.
