TABLE 1.

Liquid biopsy technologies

Biomarker	Description	Isolation techniques
Circulating tumor cells (CTCs)	Cells released from sites of primary and metastatic cancer into the bloodstream	Size‐based filtration of CTCs Immunofluorescent staining of CTCs using established epithelial or tumor cell surface markers Antibody targeting of white blood cells for removal, followed by collection of untagged CTCs
Cell‐free DNA (cfDNA)	Nucleic acid shed into circulation during cellular necrosis or apoptosis; a subset of cfDNA is derived from tumor cells, i.e. circulating tumor DNA (ctDNA)	Centrifugation for removal of cells, followed by plasma extraction of cfDNA
Extracellular vesicles (EVs)	Cell membrane‐derived particles, including apoptotic bodies, microvesicles and exosomes, that contain molecular cargoes specific to the origin cell and have important roles in cell‐to‐cell communication	Ultracentrifugation, which isolates EVs based on size and density