6. Limitations of current methods for CTC detection

In this context, one needs to keep the limitations of current methods for CTC detection in mind. Epithelial cell adhesion molecule (EpCAM)-dependent enrichment techniques are the most widely used with the CellSearch™ system being so far the only FDA-approved system [30]. However, detection of CTCs is limited by the CellSearch™ system to cells with expression of EPCAM and cytokeratin 8/18/19. Respectively, the CellSearch system can certainly miss the detection of subpopulations of CTCs with decreased epithelial marker expression as a result of CTCs that have undergone epithelial-mesenchymal transition (EMT) [31]. It was observed that tumor cells which already initiated EMT are correlated with worse prognosis and therapy resistance [32]. Therefore, many EpCAM-independent methods are currently being developed and tested for CTC characterization. Translation into clinical routine practice of these new methods seems to be currently difficult. Multicenter assessment studies are lacking, and thus their reproducibility, sensitivity and specificity remain to be evaluated.

Author details

Germany

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