Tumor Extracellular Vesicle Digital Scoring Assays for Cancer Detection and Monitoring

Tumor-derived extracellular vesicles (EVs) have emerged as promising targets for liquid biopsy, enabling noninvasive mRNA profiling to support cancer detection, staging, and treatment monitoring. This Review highlights the development and clinical translation of EV Digital Scoring Assays, an innovative class of two-step liquid biopsy platforms integrating click chemistry-mediated tumor EV enrichment (via EV Click Beads or EV Click Chips) with reverse transcription digital PCR (RT-dPCR) for absolute quantification of tumor mRNA. These assays have demonstrated clinical utility across multiple solid tumors: identifying oncogenic alterations in pancreatic ductal adenocarcinoma and Ewing sarcoma, detecting early stage hepatocellular carcinoma in at-risk cirrhotic patients, differentiating localized from metastatic prostate cancer, and monitoring treatment response in hepatocellular carcinoma. We also examine emerging technologies and parallel efforts from other groups, including microfluidic isolation platforms, PCR-free digital detection, and machine learning-based analytics. Together, these studies showcase how "enrich-then-count" strategies can overcome challenges in tumor EV specificity and transcript quantification, offering scalable solutions for precision oncology. The EV Digital Scoring Assay provides a versatile and modular platform, potentially enabling broad adoption across diverse tumor types and clinical contexts for real-time noninvasive cancer management.