Non-Coding RNAs in Cancer Liquid Biopsy: From Regulatory Networks to Functional Biomarkers for Precision Oncology

This review explores circulating and extracellular vesicle (EV)-associated ncRNAs as functional readouts in cancer liquid biopsy. We discuss their biological origin, carrier state, biofluid context, clinical applications, analytical technologies, artificial intelligence (AI)-assisted integration, standardization barriers, and regulatory requirements. The technology discussion considers sequencing, targeted amplification, and emerging direct or polymerase chain reaction (PCR)-free strategies as complementary translational routes for reliable ncRNA measurement. We propose that ncRNAs should not be viewed as alternatives to ctDNA, but as functional biomarkers that can link tumor genotype, regulatory state, and clinical phenotype within integrated multi-analyte precision oncology.