Liquid biopsy in cancer refers to the isolation and analysis of tumor-derived materials such as DNA, RNA, intact cancer cells, and extracellular vesicles (EVs) in body fluids such as blood, urine, saliva, and feces [1,2]. Solid tumors release a variety of materials into body fluids at adjacent tissue sites, and the most common are tumor-derived DNA fragments (ctDNA) or circulating tumor cells (CTCs).