Emerging Technologies for Detection of Cell-Free Tumor DNA and RNA in Serum: Towards Early Cancer Detection and Monitoring

Cell-free tumor DNA (cftDNA) and cell-free tumor RNA (cftRNA) are emerging as powerful biomarkers for cancer detection, monitoring, and prognosis. These nucleic acids, released into the bloodstream by tumor cells, carry cancer-specific genetic and epigenetic alterations and can be detected non-invasively. Detection before clinical diagnosis offers a unique opportunity for earlier intervention yet requires longitudinal cohort studies to establish pre-diagnostic biomarker profiles. Current technologies enable sensitive quantification of cftDNA and cftRNA, with spike-in controls allowing absolute quanti-fication of single nucleosome-bound cftDNA, addressing a key limitation in liquid biopsy assays. Advances such as DNA-PAINT now permit single-molecule resolution detection of point mutations and methylation patterns characteristic of cancer, while new proteomics methods can identify the tissue of origin of exosome-derived nucleic acids. This review discusses state-of-the-art detection strategies for cftDNA and cftRNA, highlights gaps in longitudinal sampling, and outlines future research directions toward integrating mul-ti-omic liquid biopsy approaches for improved early diagnosis, monitoring, and relapse detection.