Table 1. Comparison of common CTCs isolation and enrichment techniques.

Methods	Representative examples	Advantages	Disadvantages
Coated anti-EpCAM antibody	Cellsearch (FDA approved)	High repeatability and specificity	Due to EMT, epithelial specific antigens were lost, resulting in loss of capture efficiency
Size-Based selection	Isolation by size of epithelial tumor cells (ISET) [37]	Don’t rely on EpCAM antigen on the surface of CTCs	Don’t detect CTCs with a very small size
Density-Based selection	Oncoquick [38]	Preserve cell viability	Low sensitivity and unstable, Missing rare CTCs
Microfluidics	CTC-CHIP [35]	High sensitivity and high detection rate	Lack of clinical verification
immunomagnetic	Magnetic Activated Cell Sorting (MACS) [39]	Preserve cell viability and easy to count	Adsorption of non-specific cells containing target markers leads to decreased sensitivity