Liquid Biopsy in Cancer: Advances, Clinical Applications, and Future Directions

Liquid biopsy has emerged as a minimally invasive approach for cancer detection, monitoring, and treatment guidance. It enables the analysis of tumor-derived components circulating in body fluids such as blood, urine, and cerebrospinal fluid. These include circulating tumor DNA (ctDNA), cell-free DNA (cfDNA), and circulating tumor cells (CTCs), which can provide important insights into tumor heterogeneity, disease progression, and therapeutic resistance. This article discusses the principles of liquid biopsy and highlights the latest technologies used for its analysis, including next-generation sequencing (NGS), droplet digital PCR, and advanced molecular profiling techniques. The clinical applications of liquid biopsy covered in this review include early detection of cancer in healthy and high-risk individuals, real-time monitoring of treatment response, detection of drug resistance, assessment of minimal residual disease, and prognosis prediction. In addition, liquid biopsy provides a unique advantage by capturing material shed from multiple metastatic sites, thereby offering a broader view of tumor diversity compared to traditional biopsies. Limitations such as low biomarker abundance in early disease and confounding factors like clonal hematopoiesis are also addressed. In conclusion, liquid biopsy represents a transformative tool in precision oncology, offering dynamic and repeatable insights that can improve early diagnosis, personalized therapy, and long-term disease management. Future perspectives include expanding its use to other body fluids and integrating multi-omic and artificial intelligence approaches for greater clinical accuracy.