This story on a new diagnostic method in oncology is getting a lot of attention in the press. It's a collaboration between J&J, a small company they've bought called Veridex, and several oncology centers to see if very sensitive monitoring of circulating tumor cells could be a more useful biomarker.
The press coverage has some hype in it - for one thing, all the stuff about detecting one single cancer cell in the whole body isn't too helpful. The cells have to be circulating in the blood, and they have to display the markers you're looking for, to start with. But I can't deny that this is an interesting and potentially exciting field. There's some evidence to suggest that circulating tumor cells could be a strongly predictive marker can in several kinds of cancer.
These studies are looking at the sorts of endpoints that clinicians (and patients, and the FDA) all respect: overall survival, and progression-free survival. As discussed around here before, it's widely felt in oncology that these are where the field should really be spending its time, rather than on tumor size and so on. (You'd think that tumor size or number of detectable tumors would correlate with survival, but in many cases it's a strikingly poor predictor - which is a shame, since those are easier and faster numbers to get). A blood test, on the other hand, that strongly correlates with survival would be a real advance.
The value would not just be in telling (some) patients that they're showing better chances for survival, although I'm sure that'll be greatly appreciated. It's the patients whose numbers come back worse that may well be helped out the most, because that indicates that the current therapy isn't doing the job, and that it's time to switch to something else (assuming that there is something else, of course). The more quickly and confidently you can make that call, the better.
And from a drug development perspective, the uses of such assays in clinical trials are immediately obvious. Additionally, I'd think that these would be a real help to rolling-enrollment Bayesian trial designs, since you could assign patients to (and move them between) the different study groups with more confidence.
The Veridex/J&J assay (called CellSearch) uses an ingenious magnetic immunochemical approach. Blood samples are treated with antibody-coated iron nanoparticles that recognize a common adhesion protein. The cells that get bound are separated magnetically on a diagnostic chip for further immunostaining and imaging. There are other techniques out there as well - here's an article from Technology Review on a competing one that's said to be more sensitive, and here's a San Diego company trying to enter the market with an assay that's supposed to be broader-based). The key for all of these things will be bringing the costs down (and the speed of production up, in some cases). These are tests that ideally would be run early and often, so the cheaper and faster the assay can be made, the better.
Now, of course, we just need some more therapies that work, so that when people find out that their current regimen isn't working, then they have something else to try. If these circulating-cell assays help us sort things out faster in the clinic, maybe we'll be able to make better use of our time and money to that end.