Table 5.

Advantages and disadvantages of liquid biopsy components.

Component	Advantage	Disadvantage
ctDNA	Well established methods for detection of tumor-specific genetic abnormalities with greater sensitivity Analyze cancer origin and prediction of drug effectiveness Detection of acquired resistance and/or minimal residual disease Cancer progression and metastasis monitoring	Unsuitable for functional test due to impaired detectability (low ctDNA abundance) Background noise from typical cell-free DNA Difficulties in standardizing procedures
mtDNA	Compared to nuclear DNA, single cell contains several thousand copies of mtDNA Higher sensitivity Enable detection of even small amounts of molecular alterations due high mutation rate Potential prognostic marker due to differential fragmentation pattern between cancer patients and healthy individuals	Not fully characterized yet Lack of optimized protocol for cf-mtDNA Large scale prospective studies are needed
CTCs	Feasible for molecular and morphological identification Possible prognostic and/or predictive markers for monitoring cancer progression and metastasis Potential therapeutic targets Useful for in-vitro culturing to test drug sensitivity DNA, RNA and protein profiling	Low specificity- especially in early stage settings Difficulties with detection method standardization due to EMT and heterogenous biomarkers for identification Short half-life
cCAFs	Well established role in cancer progression and metastasis Advantage survival in circulation by forming clusters with CTCs and/or CSCs Potential therapeutic target Detection and monitoring of minimal residual disease Potential biomarker for early detection and prognosis Prospective model for better understanding of TME	Larger confirmatory studies are needed Lack of robust and standardized methods for detection