In an Opinion column on CNN, Dr. H. Gilbert Welch, M.P.H., a professor of medicine at the Dartmouth Institute of Health Policy & Clinical Practice and the author of
Overdiagnosed: Making People Sick in the Pursuit of Health" (Beacon Press 2011), raises questions about this simple new blood test that is able to detect minute quantities of cancer cells that might be circulating in your bloodstream.
“The conventional wisdom is people either have a disease or they do not. But, in fact, there are a lot of people somewhere in between. . . I don't know whether this test will help some patients. It might, but it will take years to figure that out... Ironically, what this test might actually teach us is that it's not that unusual for healthy people to have an occasional cancer cell in their blood.”
http://www.cnn.com/2011/OPINION/01/1...x.html?npt=NP1
Dr. Elaine Schattner pointed out that Dr. Welch may have mised the point of this technology. It was developed primarily to help oncologists monitor tumors in patients who already are known to have disease. For example, doctors could check for new, resistance-conferring mutations in patients who are already on a cocktail of meds for lung cancer.
The blood test could obiate the need for repeatedly doing CT scans and biopsies to measure disease, the extent of disease and new mutations in people undergoing cancer treatment.
The June issue of Oncology News International (June 2010, V 19, No 6) quotes a Duke University study of the use of high-tech cancer imaging, with one representative finding being that the average Medicare lung cancer patient receives 11 radiographs, 6 CT scans, a PET scan, and MRI, two echocardiograms, and an ultrasound, all within two years of diagnosis. A study co-author (Dr. Kevan Schulman) asks: "Are all these imaging studies essential? Are they all of value? Is the information really meaningful? What is changing as a result of all this imaging?"
So the investment by Johnson and Johnson, which was what the news was about, makes it more likely this will actually happen in non-research clinics. The technology has the potential to make cancer patients' lives easier and less costly and for doctors to stop giving them meds to which they've acquired resistance.
http://www.scientificamerican.com/ar...against-cancer
My comment is not really about early cancer diagnosis. It is about prognostication and drug selection with the CTC (circulating tumor cells) technique. The number of cells discovered in the CTC technique has turned out to be a good prognosticator of how well treatments are working. Monitoring CTCs could be utilized for confirmation after the patient is administered either empiric or assay-directed most beneficial therapeutic agents.
But CTCs really aren't useful with respect to drug selection. The problem is with isolating (even by size) and analying single cancer cells. The supposition is that common cancers can be detected and cured through analysis at a genetic level of a small number of cells or even a single wayward cell. CTCs are free-floating cancer cells that can remain in isolation from a tumor for over twenty years.
And what is the relationship of such long-lasting cells to the tumor cells that needed to be attacked through tested substances? And in regards to some molecular tests utilizing living cells, generally of individual cancer cells in suspension, sometimes derived from tumors and sometimes derived from CTCs, this was tried with the old human clonogenic assay, which had been discredited long ago.
One testing approach to find CTCs actually can miscount non-tumor epithelial cells as tumor cells. And 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."