Circulating Tumor Cells and Extracellular Vesicle Cargo as Dynamic Biomarkers in Cancer Metastasis and Therapy Monitoring

The detection and molecular characterization of circulating tumor cells (CTCs) and extracellular vesicles (EVs) have emerged as powerful tools for understanding cancer metastasis and monitoring therapeutic response. This review examines current technologies for CTC/EV isolation (microfluidics, nano-patterning, immunoaffinity) and analyzes their cargo (DNA, RNA, proteins, lipids) as dynamic biomarkers of tumor progression. We highlight clinical applications in breast, prostate, and colorectal cancers, where CTC counts correlate with overall survival (HR 2.1, 95% CI 1.8-2.5), and EV miR-21 predicts therapy resistance (AUC 0.82). Challenges in standardization and clinical translation are discussed, with future directions focusing on single-cell multi-omics and AI-driven analysis of vesicular cargo for real-time treatment adaptation.