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.
Filed under: Diagnosis, Management, Risk | Tagged: blood, circulating tumor cells, CTCs, HB-Chip |
THE "NEW" PROSTATE CANCER INFOLINK 
Please note that a media release about the collaboration between Johnson & Johnson and the researchers at Massachusetts General Hospital on this initiative is now available on the Johnson & Johnson web site.
Let the over-treating of many types of cancer begin. Every time one of these tests comes back positive people will be screaming to be treated and many doctors will do it — not to mention the emotional trama that will be inflicted on patients who are told cancer was found. If the theory that we all get cancer everyday and our bodies clear it is true, how will this test be able to tell the difference between a person who truly has progressive cancer and those who don’t, not to mention the cost of all the follow-up testing that will result from a positive CTC test. This test will cause way more harm than the PSA test across many other cancers
Ummm … I think we have a ways to go before before that reaction is justified … just as we have a ways to go before we can be sure what this test can actually be used to do.
Chris,
One can take your approach, but there is also a different way to look at the test, if indeed it is sufficiently sensitive and if it can report the level of cancerous cells in the body.
I can see the test being used to differentiate between cases where a high PSA is caused by cancer or by BPH or other non-cancerous causes. It could also be used to detect cancer in patients who have had a prostatectomy and should be cancer free. If the test can provide significant quantitative information, it can also be used to assist in AS.
Finally, it’s a very personal decision if you want to be treated or not. We know of a very well-known doctor who brags he doesn’t want to know his PSA. I and many others, on the other hand, are in favor of being tested in order to make an intelligent decision on treatment (or not).
I can see the value in post-RP use. I guess. Maybe what we really need is a filter system to catch these cells and we all go in and get our filters changed periodically. That might go further in catching cells running around the body before they get a chance to lodge someplace and duplicate.
Sounds like a good plan. Looks like changing oil in my car. I wonder if it will also take 30 min and cost $39.99
:-)
I would hope that research would be done on the best usage of this test prior to it’s release.
If we can identify the cells that cause metastases and also identify which treatments work on those cells and which treatments do not then maybe we can streamline the treatment process and men could avoid drugs that may not be a benefit for their overall survival. It is not the answer but could potentially be a good tool for both the patient and the doctor in the decision-making process. Seems like it needs more research to identify best uses before it becomes commercially available. At the CMS meeting on Provenge there was a question about samples taken for identification of which men had the best response to the treatment. If companies are asked to do this in the future then, if I have read the information correctly, this test has a better chance of being helpful to men dealing with prostate cancer. When I did a Google search of circulating tumor cells I was amazed at how often the words prostate cancer also were in the links. Seems to be an area of interest to researchers.
Kathy: It is very clear that there may be several years-worth of work to be done before this test comes to market (always assuming it ever does). There was similar hype around the original RT-PCR test many years ago. It proved to be too sensitive to actually tell anyone anything clinically significant, and the data was rarely capable of being replicated with accuracy. However, it is true that there is considerable interest about CTCs among the specialist medical oncologists who are heavily involved in the development of next-generation therapies for late stage prostate cancer (Scher, Hussein, Higano, Armstrong, et al.).
Is this the chip that goes into the arm that puts out medicine if you have prostate cancer? What are the side effects of this chip and what are the known malfunctions of the chip?
Michelle:
No. The chip referred to in this article is a diagnostic chip, used in a diagnostic laboratory. It is not implanted in patients at all.
The device you are referring to is not a chip. It is a long-term drug depot system used to slowly release a drug called Vantas (histerelin implant) over the course of a year. To find out more about the Vantas implant, you can click here.
However, the Vantas Implant system is only one of several types of delivering hormone therapy (aka androgen deprivation therapy) for men with prostate cancer. Others are easier to give to the patient but only last for 3, 4 or 6 months, so they have to be given more often.