Liquid Biopsy: A Breakthrough Technology in Early Cancer Screening

Cancer is the leading cause of death globally, with nearly 20 million new cases and 9.7 million deaths in 2022. Due to its vague initial symptoms, cancer is often difficult to detect in its early stages. Liquid biopsy, a revolutionary approach in oncology, provides a minimally invasive, real-time method for cancer detection, monitoring, and characterization by examining circulating tumor components in body fluids. This review presents current technologies and clinical applications of liquid biopsy, focusing particularly on its value for early cancer diagnosis. Liquid biopsy enables molecular profiling of cancer for precision oncology by isolating circulating extracellular nucleic acids (cell-free DNA), circulating tumor DNA, and circulating tumor cells from blood and other body fluids. Cell-free DNA, which circulates freely in the blood, may or may not be tumor-derived, while circulating tumor DNA is specifically of tumor origin. Additionally, circulating tumor cells can be isolated from blood; these cells, shed from tumors into the bloodstream, typically survive only 1–2.5 h before immune clearance, though a small fraction can persist and metastasize to distant sites. Exosomes, small membrane-bound vesicles secreted by tumor cells, also carry molecular information about the tumor and have become a valuable source of biomarkers in liquid biopsy. Advances in detection technologies for these analytes have expanded the utility of liquid biopsy, facilitating the identification of somatic mutations and actionable genomic alterations in tumors. Finally, this review discusses the opportunities and challenges facing liquid biopsy and offers insights into its future development.