Detection of circulating tumour cells in colorectal cancer: Emerging techniques and clinical implications

Table 2 Studies showing postoperative isolation of circulating tumour cells in colorectal cancer–markers, techniques, and clinical implications

No.	Technology	Markers	Number of patients	TNM stage	Correlation	Clinical significance	Ref.
1	CellSearch system	EpCAM	164	I-III	With stage	N/A	[60]
		EpCAM	24	IV	With therapy response	May be used in monitoring response to therapy	[61]
		EpCAM	97	II	With stage	Correlates with stage	[62]
		CD133+, CD54+, CD44+	15 (nmCRC); 95 (mCRC)	I-IV	≥ 5 CTCs were 8 times more likely to develop distant metastasis. CTC counts show good correlation with colorectal neoplasm	Independent prognostic marker for nmCRC	[63]
		hTERT, CK19, CK20, CEA	438	I-III	-	Poor relapse free survival	[64]
		hTERT, CK19, CK20, CEA	157	I-III	With stage	Poor relapse free survival and overall survival	[65]
		Survivin, CK20 and CEA	156	I-III	With stages (Duke’s) and lymph node metastasis.	Useful as an adjunct in detection of CRC patients	[66]
		CD133, CEA, CK20, CK19,	197	II-III	CEA/CK/CD133 expression and stage (Duke’s)	Prognostic significance (Duke's stages B and C)	[44]
		hTERT, CK-19, CK-20, CEA, GAPDH and mRNA	72	I-IV	CEA, mRNA: With stage, vascular invasion, and postoperative metastasis	Prognostic and predictive	[67]
2	Flow-cytometry with immunofluorescence	CTCs	18	I-III	With stage and also detected in an early cancer stage.	Predictive	[68]
3	Pyrosequencing	KRAS (Codon 12/13)	26	IV	No association	Prognostic	[69]
4	MetaCell separation method	CTCs	98	I-IV	CTC-positive in 83%	Prognosis and predictive	[70]
					CTC-negative in 17%
5	Mag Sweeper	PIK3CA	242	-	Mutational discordance found between CTCs, DTCs, and metastases, and among CTCs; DTCs from this patient propagated in vitro contained a PIK3CA mutation	Investigating new drug therapies	[71]
6	CTC-Chip	EpCAM, HER2, and EGFR	-	-	Efficiency of 87.5%	In situ protein expression, and culture CTCs from the same set of cells	[72]

CRC: Colorectal cancer; DTC: Disseminated tumour cells; GAPDH: Glyceraldehydes 3-phosphate dehydrogenase; nmCRC: Non-metastatic CRC; mCRC: Metastatic CRC.