Table 1 Differences between CTC and ctDNA analyses
| Â | CTC | ctDNA |
|---|---|---|
Equipment | Special instrumentation for cell identification needed | None, simple blood collection |
Isolation of CTC or ctDNA | Complex CTC isolation out of thousands of cells and complex single-cell transfer for further processing | No isolation of ctDNA required; instead, standard preparation of plasma DNA |
WGA required for DNA analysis | Yes | No |
Information on heterogeneity and clonality | Yes, if enough CTCs are captured and successfully analyzed | No, results represent an average from all cells shedding tumor DNA into the circulation |
Dependence on EpCAM markers | Yes, for most CTC capture systems, such as the CellSearch system. EpCAM-independent CTC capture systems exist but await validation in clinical studies | Independent of any marker |
Applicability for basic metastasis research | Instrumental, as it enables cell-by-cell analyses, generation of cell lines and analyses in animal models | Provides only a snapshot of the current status of the tumor genome |
Applicability for diagnostic or monitoring purposes | Established for CTC enumeration; advancements will depend on improvements in CTC capturing, analysis tools and associated costs | Appears to be very attractive because of the simplicity of obtaining plasma DNA; needs to be determined in clinical studies |