Liquid Biopsy for Cancer Detection: Biology, Clinical Applications, and Future Horizons

Liquid biopsy has emerged as a transformative tool in oncology, offering a minimally invasive method for detecting, monitoring, and understanding cancer through biomarkers circulating in body fluids, such as blood, urine, and saliva. Unlike traditional tissue biopsies, which are invasive, risky, and often limited by sampling errors, liquid biopsy enables dynamic and real-time insights into tumour evolution. This review comprehensively explores the biological basis, technological innovations, and clinical applications of liquid biopsy, with a focus on circulating tumour DNA (ctDNA), circulating tumour cells (CTCs), and exosomes. We also highlight emerging analytes, such as tumour-educated platelets and cell-free RNA. The human dimension of liquid biopsy is emphasised, underscoring its potential to reduce the patient burden, democratize access to diagnostics, and align science with compassion. Finally, we discuss challenges, ethical considerations, and future directions, envisioning a healthcare landscape in which a simple blood draw could replace invasive procedures and transform patient outcomes.