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

Table 3 Circulating tumour cells in metastatic vs non-metastatic colorectal cancer

No.	Type of CRC	Markers used	Detection method used	Relevance	Clinical implications	Limitations of the study	Ref.
1	nmCRC	CEA, CA19-9, CA72-4	Cyttel	Diagnostic/prognostic/predictive	Combination of CTCs and CEA: Diagnostic and prognostic indicators	Small sample size, weak power of the study	[73]
2	mCRC	CK, CD45	Immunomagnetic separation	Prognostic/predictive	The number of CTCs before and during treatment is an independent predictor of PFS and OS in patients with mCRC	The baseline unfavourable CTC was low (26%) and overall CTC yield was less than in other epithelial cells	[74]
3	mCRC	ALDH1, CD44, CD133, MRP5, Survivin	qRT-PCR	Prognostic	Poor prognosis and chemo therapy non-responsiveness	Require further molecular analyses of CTCs for selection of targeted agents	[75]
					Survivin and MRP5 selection of mCRC patients resistant to 5-FU and L-OHP
4	mCRC	CEA	Cyttel method, immunofluorescence in situ hybridization technologies (imFISH)	Prognostic	PFS, OS	Small sample size	[6]
						Lack of dynamic enumeration of CTCs
5	mCRC	VEGF, CD133+, CD34+/KDR + EPC, CD-34-VEGFR2	Flow cytometry/IHC	Prognostic	Treatment response; PFS, OS	-	[76]
6	nmCRC	CD133, CD166, CD44, EpCAM, ALDH1	Tissue microarray, IHC	Prognostic	No association with poor clinical response; OS	Treatment information was missing (local recurrence, distant metastasis, and postoperative therapy)	[77]
7	nmCRC	CK19, MUC1, CD44, CD133, ALDH1	Flow-cytometry, CellSearch, Cytomorphology, qPCR	Prognostic	May be useful as a therapeutic target; PFS, OS	-	[78]

CRC: Colorectal cancer; nmCRC: Non-metastatic CRC; mCRC: Metastatic CRC; OS: Overall survival; PFS: Progression-free survival; IHC: Immunohistochemistry.