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Page 2 of 18 Malentacchi et al. J Cancer Metastasis Treat 2020;6:34 I http://dx.doi.org/10.20517/2394-4722.2020.34

Figure 1. Schematic overview of LB biospecimen, biomarkers, and their clinical applications in EC. Modified from Muinelo-Romay et al. [24] .
LB: liquid biopsy; EC: endometrial cancer

Moreover, traditional biopsy is invasive, it is neither feasible nor practical to perform serial biopsies to
guide treatment in real time, and, depending on the site of tumor, biopsy cannot be performed.

Liquid biopsy (LB) has the potential to overcome many of the limitations of traditional biopsy since it is
highly tailored and minimally invasive, can be repeated several times, is a cost-effective method, and can
be used to screen and monitor response to treatment and to identify the clones involved in the relapse,
metastasis, or resistance to treatment. However, many challenges still need to be overcome before LB
[1]
becomes a reliable and widely available option .
LB is represented by fluids that can be collected from the body such as blood, urine, cerebrospinal fluid,
[2]
lavages, peritoneal fluids, and saliva , and the related biomarkers are, consequently, circulating tumor
markers such as circulating tumor cells (CTCs), nucleic acids, proteins, and metabolites deriving from
tumors.

LB usually refers to blood or blood compounds, and the principal biospecimens analyzed are circulating
tumor DNA (ctDNA), CTCs, and proteins. Proteins were the first molecules analyzed within blood and
other body fluids before the invention of LB [e.g., CA125 in peripheral blood (PB) for ovarian cancer].
Nowadays, the target biomolecules are increasing and include microRNA (miRNA), lncRNA, miRNAs,
vesicles, and platelets [Figure 1].