I remember the first time I heard the hype on CTCs, about 8 years ago, when I was in pharma and we were using it as an exploratory marker. Things have not moved much since then, as far as I can tell. It is still in the research mode, slowly moving into clinical use, but a number of barriers remain - standardization (what is a CTC? What is the best way to extract them? There are so many conflicting technologies, it is difficult to compare data), convincing clinical trial data, etc. In short I think it will remain mostly research in the short and medium term.
Here's a brief summary of the problems faced by a company in the space: http://lifescivc.com/2013/04/on-q-ity-a-cancer-diagnostic-company-r-i-p/