Circulating Tumor Cells (CTC) and Tumor-Derived Extracellular Vesicles (tdEV)

The observation that increasing circulating tumor cell (CTC) and tumor-derived extracellular vesicle (tdEV) load is directly related to worse clinical outcome of cancer patients is in line with expectations. However, both CTC and tdEV exhibit inter- and intra-patient heterogeneity, and the puzzle is yet to be deciphered in regard to the phenotype of CTC or tdEV that can predict prognosis and response to therapy or an effective treatment. A large variety of different approaches to identify CTC and tdEV have emerged over the last two decades, some of which have been evaluated in the clinic, whereas others not. In the second case, we can just speculate what is the output of these techniques and how it is translated to better understand the metastatic process and guide cancer patient care more effectively. Here, we will review what we have learned from CTC and tdEV identified by the CellSearch system and discuss our initial attempts to further characterize tdEV and explore their potential.