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New, chip-based technology can isolate, identify prostate cancer cells in blood

Posted Jan 03 2011 12:00am

According to an Associated Press story that came out this morning, Johnson & Johnson and “Boston scientists” are working together on “A blood test so sensitive that it can spot a single cancer cell lurking among a billion healthy ones.” It goes on to state that, “A test that can capture such cells has the potential to transform care for many types of cancer, especially breast, prostate, colon and lung.”

There is no doubt that the ability to identify and isolate specific types of cancer cell (circulating tumor cells or CTCs) from a patient’s blood with this level of sensitivity and accuracy would have all sorts of potential scientific and clinical value. However, before we get carried away and think that this necessarily offers a whole new way to screen for prostate cancer, let’s just take a step back.

If one can identify and isolate prostate cancer CTCs in someone’s blood, what does this actually mean? Well it certainly means that prostate cancer cells have been able to escape from the prostate. So the question then arises … If we can identify such cells in a man’s blood, does that man already have metastatic disease? Well obviously, yes, maybe it does. But also, no, maybe it doesn’t.

We make mutated (potentially cancerous) cells all the time. Those cells sometimes escape from the tissues in which they developed and move into the bloodstream. And in many of us those cells are effectively identified and eliminated by our immune systems, or they die because they are unable to move to a find a suitable environment in which to develop and grow. So the presence of a single prostate cancer cell in the bloodstream is not necessarily indicative of clinically significant prostate cancer.

On the other hand, in a man who already has a diagnosis of prostate cancer, the ability to identify prostate cancer CTCs in the bloodstream at above a certain level is likely to be indicative of a very early stage of metastatic disease. Conversely, the ability to identify prostate cancer CTCs in the bloodstream at below a certain  level may be a better indicator of the need for a biopsy than a PSA test.

The image below shows (on the left) a cluster of circulating prostate cancer cells isolated from the blood of a patient with metastatic prostate cancer using (on the right) the new “herringbone” chip technology already being referred to as an HB-Chip. A paper published last October by Stott et al. describes the use of this chip technology to isolate and identify CTCs.

We do already have one test that is approved for and used to identify CTCs in men with advanced forms of prostate cancer the CellSearch test . However, the sensitivity of this test is not great, and as far as prostate cancer is concerned this test is currently only known to be useful as a way to assess clinical responses to treatment in men with very late-stage disease. We undoubtedly will need a good deal more data before we can best understand how to use the new HB-Chip test in the diagnosis, prognosis, and treatment of prostate cancer. Whether it can really live up to some of the hyperbole in the Associated Press story (which is presumably based on a media release from somewhere that we have yet to identify) is a different question.

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