Liquid biopsy: An innovative tool in oncology. Where do we stand?

The Liquid Biopsy (LB) represents an ideal surrogate of tumor Tissue Biopsy (TB) when the aim is to obtain useful information on patient prognosis and personalized therapy. This technique renders it possible to isolate circulating tumor cells, circulating tumor DNA and other molecules from biological fluids. The most commonly used fluid for liquid biopsy is blood, but depending on the case it could be necessary to isolate the tumor components from other biological fluids such as urine, pleural effusion, cerebrospinal fluid, and others. The main advantages of liquid biopsy are the minimally invasive nature of the procedure and the possibility of analyzing all tumor clones. Limitations include difficulties in the isolation of tumor components and the requirement for highly sensitive analysis methods to avoid the risk of technical artifacts. In our review we will focus on describing circulating tumor biomarkers to illustrate the variety of information that can be obtained from biological fluids, particularly blood. We will then discuss the advanced biotechnological techniques suitable for the identification and analysis of Circulating Tumor DNA (ctDNA), examining both the potential and limitations of analytical methods and the clinical applicability of liquid biopsy for cancer diagnosis, monitoring, and therapeutic prediction. Additionally, we will explore strategies to enhance this valuable alternative to the more invasive tissue biopsy, with a dedicated focus on ongoing clinical studies, currently approved tests, and guideline recommendations.