Table 1.

Merits and drawbacks in three different methods for CTCs expansion

Method	CDX	Short term	Long term
CTC number	High	Low	High
Patient origin	Advanced stage only	Early and advanced stage	Advanced stage only
Condition	Experimental animal	10% FCS medium	Defined serum-free medium
Sample origin	Organ-vasculature circulation	Peripheral venous or arterial circulation	Peripheral venous or arterial circulation
Character	Tumorigenic capacity evaluation; complex procedure and individual difference	Differentiation and limited proliferation ability with significant phenotypic alterations	Phenotype stable; maintaining the tumorigenicity in non-adherent status
Research purpose	Simulate microenvironment in vivo	Expand enough CTCs for downstream analyses	Enrich and expand CTCs to establish patient-derived cell lines for long-term research
Cost	High	Cheap	Moderate
Culture cycle	Several months	1-2 weeks	Several months −1 year
Successful rate	Low	Moderate	Low