Detecting and Analyzing Circulating Tumor Cells
Detecting and analyzing circulating tumor cells in the peripheral blood of patients with advanced cancer has in recent years increasingly come into the scientific focus. The quantification of such CTCs has proven useful in metastatic breast, colon, and prostate cancer. Meanwhile, interest has expanded from the quantification of such CTCs to a precise molecular characterization thereof, especially with regard to targeted therapies. A genetic analysis of the CTCs and their subpopulation opens up the possibility to search for new vantage points for treating occurring resistances. CTCs are thus a particularly valuable biological sample if tissue samples are not available. This is why one refers to “liquid biopsies” in this case. They allow for repeated checks of the progression of the disease to identify the current tumor biology (real-time analysis).
The CTC testing methods are highly variable and the choice of testing method depends on the type of primary cancer and the desired examination. For epithelial tumor CTCs (carcinoma), we have developed and validated a real-time PCR test for molecular quantification (cf. relevant literature on the issue). This testing method includes a previous enrichment of the epithelial tumor cells via paramagnetic beads (magnetic cell sorting). These beads are coated with the kind of antibodies targeted against one of the most common surface antigens (EpCAM) in CTCs of epithelial origin (see image). If the CTCs are primarily to be characterized on a molecular level (for instance gene amplification assays (FISH) or mutational analysis), other means of testing such as filtration are used.
Most of the testing methods require EDTA-treated blood.
Duration of Testing
In cases of simple molecular quantification of the CTCs, results are available after five days. When using the complex procedures such as mutational analysis, the results will be available within two weeks at the latest.
Literature on the subject