Circulating Tumor Cells

CTCs are cells that a primary tumor sheds into the bloodstream or lymph system and these are the cells that can form metastasis, even after the primary tumor is removed. They can potentially play an important part in disease progression which is why many clinical trials have begun tracking them. I have seen a few clinical trials now that are designed to show whether there is a link between the number of CTCs and people who's cancer recurs versus those that remain disease free.

Even though this concept of CTCs is new in North America, it is something that has been done for a number of years already in Europe. Maintrac, which is the lab that did my chemo sensitivity testing, also measures circulating epithelial tumor cells and is one of the methods that can be used to track them. Cell Search is another system that measures CTCs and is the only one that is FDA approved. From what I have read, the number of cells detected by both systems can be drastically different which is why it is good to pick one and stick to it. The reason I chose Maintrac is because they claim to have the most sensitive CETC counting system in the world. They do not "touch" or extract the cells so this way no cells are lost when being processed. That is why the number of CTCs they report will be significantly higher than Cell Search. They also do not work with cut-offs to determine prognosis, only an increase or decrease in cell numbers. Cell Search on the other hand uses ≥5 CTCs as the cutoff for unfavorable prognosis.

Although it is approximately $350 each time you test, to me this seemed like a good way to gauge what was happening in my body post treatment. Unfortunately, rather than seeing a decrease in cell numbers which is the desired outcome, the two tests I have done showed an increase in cell numbers. I did one post radiation as a baseline, another 3 months later and in that timeframe, the cell count more than doubled. Fortunately this was caught early which is the intention of monitoring CTCs but these results together with the positive Oncoblot are a clear sign that I need to take action now.