[gdpawel]

The number of cells discovered in the CTC technique has turned out to be a good prognosticator of how well treatments are working. But CTCs really aren't useful with respect to drug selection. CTCs are free-floating cancer cells that can remain in isolation from a tumor for over twenty years. What is the relationship of such long-lasting cells to the tumor cells that needed to be attacked through tested substances? What if you miscount non-tumor epithelial cells as tumor cells? Also, highly invasive cells may not be detected if you are looking for epithelial antigens because the CTC also goes through a phase called "epithelial to mesenchymal transition", where you will miss locating that tumor cell if you are targeting the antigen. The key is to look for the tumor cell and not something else that "hangs with the tumor cell."