Liquid biopsy in gastrointestinal oncology: clinical applications and translational integration of ctDNA, CTCs, and sEVs

Abstract

Background and aims: Liquid biopsy offers a minimally invasive tool to detect actionable mutations, monitor minimal residual disease (MRD), and guide therapy in gastrointestinal (GI) cancers. We critically review the clinical utility of circulating tumor DNA (ctDNA), circulating tumor cells (CTCs), and small extracellular vesicles (sEVs) across GI malignancies and propose a framework for their integration into clinical practice.

Methods: We synthesized evidence from over 200 studies, including prospective trials and translational research, to assess diagnostic accuracy, prognostic value, and clinical actionability of each biomarker type in esophageal, gastric, colorectal, pancreatic, hepatocellular, and biliary cancers.

Results: ctDNA has shown strong potential for MRD detection and treatment monitoring, particularly in colorectal and pancreatic cancer. CTCs offer insights into metastatic risk and therapeutic resistance, while sEVs provide molecular cargo relevant to immunomodulation and disease progression. Emerging microfluidics and AI-driven multi-omics approaches may overcome current limitations.

Conclusion: The integration of liquid biopsy technologies into GI oncology holds promise for early detection and precision therapy. We propose a five-phase clinical roadmap and outine the key research gaps that need to be addressed before widespread implementation in routine care.

Keywords: circulating tumor DNA (ctDNA); circulating tumor cells (CTC); extracellular vesicles (EVs); gastrointestinal cancer (GI); liquid biopsy.

Graphical abstract illustrating the role of liquid biopsy in the management of gastrointestinal cancer. Tumor-derived biomarkers, including circulating tumor cells, extracellular vesicles, and circulating molecules, can be detected in different biological fluids (blood, saliva, urine, cerebrospinal fluid, seminal fluid, nipple fluid, ascitic liquid, tears, and breath) through molecular analysis. Liquid biopsy enables early detection, longitudinal monitoring, and the development of personalized therapeutic strategies. Key translational aspects include the establishment of a clinical roadmap, preclinical and analytical validation, implementation of standardized guidelines, integration of artificial intelligence and multi-omics approaches, as well as surveillance and adaptive management.

FIGURE 1

Fraction of Liquid Biopsy derived from body fluids. Overview of biological fluids utilized for diagnostic and research purposes. The outer ring identifies different types of biological fluids, including seminal fluid, tears, ascitic liquid, urine, breath, nipple fluid, saliva, blood, and cerebrospinal fluid. The inner section highlights key circulating components present within these fluids, such as circulating tumour cells (CTCs), circulating molecules (e.g., DNA, RNA, and proteins), and small extracellular vesicles (sEVs), that are obtained from liquid biopsy.

FIGURE 2

Schematic diagram outlining a unified workflow for isolating circulating tumour cells (CTCs), small extracellular vesicles (sEVs), and circulating tumour DNA (ctDNA) from blood samples. Magnetic beads functionalized with silica or sequence-specific ligands enhance biomarker recovery and shorten processing time. Advances in droplet microfluidics, nanopore sequencing, and integrated microfluidic devices enable sensitive and reproducible detection of rare variants and methylation signatures across all biomarker classes.

FIGURE 3

Flowchart illustrating the proposed clinical roadmap for integrating liquid biopsy in gastrointestinal cancer management. The diagram outlines five sequential phases: (1) analytical validation; (2) clinical validation and threshold definition; (3) guideline development and training; (4) multi-omics and AI integration; (5) adaptive surveillance and therapeutic adjustment.