Clinical relevance of circulating molecules in cancer: focus on gastrointestinal stromal tumors

In recent years, growing research interest has focused on the so-called liquid biopsy. A simple blood test offers access to a plethora of information, which might be extremely helpful in understanding or characterizing specific diseases. Blood contains different molecules, of which circulating free DNA (cfDNA), circulating tumor DNA (ctDNA), circulating tumor cells (CTCs) and extracellular vesicles (EVs) are the most relevant. Conceivably, these molecules have the potential for tumor diagnosis, monitoring tumor evolution, and evaluating treatment response and pharmacological resistance. This review aims to present a state-of-the-art of recent advances in circulating DNA and circulating RNA in gastrointestinal stromal tumors (GISTs). To date, progress in liquid biopsy has been scarce in GISTs due to several issues correlated with the nature of the pathology. Namely, heterogeneity in primary and secondary mutations in key driver genes has greatly slowed the development and application in GISTs, unlike in other tumor types in which liquid biopsy has already been translated into clinical practice. However, meaningful novel data have shown in recent years a significant clinical potential of ctDNA, CTCs, EVs and circulating RNA in GISTs.