Liquid biopsy for the management of gastrointestinal cancers

Gastrointestinal (GI) cancers rank among the deadliest types of cancers. Early detection of these cancers may play a crucial role by providing useful guide for the real-time administration of anticancer treatments. The sensitivity and specificity of the current markers used for the diagnosis of affected GI cancer patients are comparatively limited, especially for the early screening and accurate diagnosis. Liquid biopsy refers to the collection of pathological specimens from non-solid sources, as compared to the surgical excision of tissues or cells used for the conventional tissue biopsies used for the diagnosis of solid tumors. Circulating tumor cells (CTCs), circulating tumor DNA (ctDNA) and cell-free nucleic acids (cell-free DNA [cfDNA] and cell-free RNA [cfRNA]), as well as circulating non-coding RNAs can be detected and analyzed by acquiring liquid biopsy sources from patients. The minimally invasive feature of liquid biopsies, in addition to the feasibility of frequent analyses, and the extent of precise data they can provide suggest them as promising tools for the diagnosis and monitoring therapeutic response in patients with GI cancers. This review highlights the technologies used for the detection and quantification of main liquid biopsy materials, discusses their clinical significance, and addresses current limitations. The focus is on the diagnostic and prognostic opportunities of liquid biopsies in managing human GI cancers.