If this works out, it could save tremendously on resources–and more importantly, help catch cancers very early and gauge the effectiveness of ongoing treatments.
Like all modern medical advances, I’ll bet animal research was part of the equation.
Monday, January 3, 2011, 8:36 PM
Wesley J. Smith
January 3rd, 2011 | 9:33 pm
[...] This post was mentioned on Twitter by Vince Humphreys and others. Vince Humphreys said: SHS: Cancer Blood Test Could Save Lives–And Money http://bit.ly/h6T2aE #tcot [...]
January 3rd, 2011 | 9:34 pm
Despite the obvious appeal of a “blood test for cancer”, such screening tests are fraught with the hard reality of statistics: when applied to large populations with a fairly small incidence of a disease, even a tiny percentage of false positive and false negative results (inevitable in even the most accurate of tests) result in massive numbers of people who require expensive (and often risky) testing for a disease they don’t have, and a surprisingly large number of people with the disease who get missed. For more detail, see this post of mine from several years ago.
Wesley J. Smith Reply:
January 4th, 2011 at 1:21 am
I am noticing a move against cancer screening, after we have seen such a push for it. Mammograms, PSA tests, blood tests, etc., we are being told, may do more harm than good. The issue seems to be false positives. But isn’t it better to have a false positive than not catch a real positive? Color me perplexed.
January 4th, 2011 | 12:03 am
Dr. Bob -
I’m curious about more information. I live in Houston, and our MD Anderson Cancer Center is performing clinical trials on people with lung cancer to work on the cancer detection in the blood stream. According to the local ABC news network (and I’m paraphrasing from memory – any errors are all my own), the blood test would separate out and locate a single cancer cell amid all the healthy cells, letting doctors know not only that there is cancer present, but what kind of cancer it is and how best to treat it.
Given that I passed science because I eschewed biology for geology labs, I don’t know diddily about the specifics, so I’m a little confused on how your post relates to this particular study, but I’m very curious to learn more.
Wesley, not only is this a boon for all mankind, but imagine the potential to treat animals as well! Feline Leukemia claimed a number of my four-legged children in my lifetime. If animal testing leads to my vet being able to use a similar technology to check for and possibly combat feline leukemia, then any rescue animals I adopt have a better shot at living longer, healthier lives.
I hope there *was* animal research involved. As stewards of the planet, we have a responsibility to wisely use the animals here, not only for our benefit, but also to improve the quality of *their* lives. The more we know, the better we can care for them as well.
January 4th, 2011 | 11:35 am
Oh my Thor.
There is a difference between a screen and selection (everyone should know the difference had they been paying attention during the classes covering evolution). This method is based on selection, not screening!
The report said this test is based on SELECTION of CTCs (circulating tumor cells). CTCs are very rare in people without “cancer” (technically we all have cancer in our bodies). In fact, I’ve only heard (not verified) of exceedingly rare instances where “healthy” people have CTCs. In people with metastatic cancer, CTCs are STILL rare – only about 1 haematological cell in a billion is a CTC.
So, the obvious question becomes, can we select for these CTCs. Yes, we can.
How do we do this? Use an affinity method coupled with microfluidics. Use an antibody-antigen microfluidic device to pass blood cells over a surface and select for CTCs. How is this done? Coat a surface with anti-EpCAM antibodies – these are antibodies raised against EpCAM, epithelial cell adhesion molecule. EpCAM is a protein antigen (something antibodies love to bind) made by CTCs (among other cells). So, we have a molecule (anti-EpCAM) on a silicon surface that specifically binds to a chemical on a cell surface (EpCAM). Now we can select cells that make this EpCAM, by using anti-EpCAM on a silicon surface. Once we’ve captured these cells, we can double check them to see that they are CTCs. This can probably be done through staining and hybridization, etc, by using KERSMCR or DAPI, etc. This is a trivial step to the technology.
Under certain laminar flow conditions, you could probably use whole blood from a person, making this test simple.
Was “animal research part of the equation”? Define “animal research” and define “part of the equation”. No doubt people were used – you’d have to check with human blood – humans are animals. The antibodies used on the chip are probably derived from mice.
I’m also willing to bet the scientists used somewhere between 10 and 100 “healthy” patients and had zero false positives, but I’ll have to check the papers to be sure.
We should move against cancer screenings. We should advance technology that focuses on selection, instead. Like evolution, selection is far more powerful.
January 4th, 2011 | 2:44 pm
False positives lead to further diagnostic tests, and some, such as biopsies, can have significant complications. For example, less than half of men with elevated PSA actually have cancer. A small percentage (1-4%) of men who end up having a prostate biopsy end up in the hospital with complications (usually an infection). Some die (0.1% in one study). In the US, if you were to screen 100,000,000 adult men, and 10% had elevated PSA, and those 10,000,000 were biopsied, you could expect 100,000 to 400,000 to be hospitalized and over 1000 could die, not having prostate cancer.
Some screens have potential harm (e.g., radiation) that must be considered when screening millions. The challenge is to balance the benefits of screening with the risk and cost of unnecessary procedures and any inherent cost and risk of the screen itself.
As we gather more high-quality evidence concerning medical care will need to re-evaluate strategies.
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