Slashdot Mirror
A Breathalyzer For Cancer
Tiger4 writes "Cancer researchers in the UK have come up with a way to sniff for lung cancer on the breath. 'From the results, the researchers identified 42 "volatile organic compounds" (VOCs) present in the breath of 83% of cancer patients but fewer than 83% of healthy volunteers. Four of the most reliable were used to develop a nine-sensor array made from tiny gold particles coated with reactive chemicals sensitive to the compounds.' Other sources have picked up the story as well. Obviously, this would be a big breakthrough for rapid screening, and early detection significantly improves outcomes."
There's a cat that seems to be able to tell when someone is about to die.
Let me introduce you to my friend Reverend Bayes.
I didn't know that it was illegal to drive while suffering with cancer...
Ken
"present in the breath of 83% of cancer patients but fewer than 83% of healthy volunteers" So, 83% of people with cancer have this chemical, and 82% without cancer can also have it. That test will still leave 17% false negatives and then it would give false positives to nearly everyone else.
So, next time you get pulled over:
"Sir, were you aware of how fast your cancer was progressing?"
Non-oncs generally don't understand that a whole lot of cancer is "clinically irrelevant". That is, it would never go on to kill you. Thus, as early detection gets better in most areas, you detect a greater percentage of cancer that was never going to hurt the patient. However, once you see the cancer, you are duty-bound to slash/burn/poison (Susan Love's famous chapters) to cure it. Statistically speaking, you know you are actually harming some patients, but it is a dilemma -- you hurt all the patients in order to serve a greater good for some percentage of them. A good example is the growing backlash against general PSA screening. Even just a biopsy for prostate cancer can't be 100% risk-free, but the treatment is really risky, assuming you're not enthusiastic about being impotent and/or incontinent for the rest of your life.
So don't get too excited about increased early detection of cancer. Currently, it is usually a double-edged sword that brings suffering to some percentage of patients who would have avoided it before the new test existed. An exciting development would be a detection test for distinguishing cancer that's just sitting there from cancer that's on the move and likely to kill.
First of all, not all lung cancer is caused by smoking, just as not all smokers get lung cancer. Secondly, perhaps we could give the benefit of the doubt to the cancer researches and to the scientific method that they must have employed. Put another way, if you were able to think of this, you can be sure they would have realized early on that smoking might be a variable to take into account.
the scientific method that they must have employed
Quote from FA: "Moreover, in a break from the convention in medical innovation, the researchers claim that full clinical trials may not be necessary to take this new technology to a stage where it is hospital-ready. They believe instead that they could prove the device's accuracy using a series of "artificial mixtures" of particulates that could simulate cancerous and healthy breath. "
In short: We are only in it for the money.
CC.
TaijiQuan (Huang, 5 loosenings)
It should be obvious now that our bodies have cells that replicate. Sometimes the replicas are perfect but occasionally they are not. After a certain number of replications the errors add up. Most errors are benign but a small fraction are not. With billions of cells replicating there's a statistical certainty that if you don't die of something else then cancer will get you.
The preventative for cancer is to have cells that replicate perfectly, or to not have cells that replicate.
Help stamp out iliturcy.
Let me re-phrase that...
"This is a story about a way to patent and monetize something that can be done on the cheap already."
they may only be detecting those individuals who smoke vs those who dont.
About a quarter of Israelis smoke overall. About 11% of those - with a strong correlation toward heavy smokers - will eventually get cancer. About ten percent of those will continue to smoke. If that were the case, given 40 diagnosed patients and 56 healthy ones, their results would be statistically identical between groups. The results were not. Therefore, I'm guessing that your guess is simply some unreasoning dislike for tobacco users rather than a reasoned critique of the methodology. In fact, assuming the data aren't fudged, it's statistically much more likely that you, a nonsmoker (I assume), will get lung cancer than that their technique only identifies smokers.
Just recentely an article was published about the effects of a "non-perfect" screening test on a large group of people. (They did a case study for a specific test, which gives the same results as the theoretical example below)
If you have a test that is 99% accurate and 1 in 1000 people have the illness, for every million people, you'll find 990 out of a thousand who DO have the disease. And you send home 10 people who do have the disease. Too bad, 990 got the proper treatment. Right? No! Of the 999000 who don't have the disease, you'll find 9990 people with positive results. Are they getting treated? Are there risks to further tests? (for example X-rays create a risk for cancer later on.... )
And finding the 990 people WITH the disease from the 10980 people who tested positive is going to be a hassle. And costly.
Now a test with a 99% accuracy is pretty good compared to this test. As I read the slashdot intro, there is a 17% false negative rate, and up to 82% false positve rate....
If that was the case then assuming their detector is perfect at detecting "was or is a smoker" they'd have a 63% false negative rate and a 30% false positive rate.
If they perfectly detected "is currently a smoker" they'd have a 100% false negative rate and a 30% false positive rate.
So your guess is completely off the mark.
Numbers from: http://www.nature.com/nnano/journal/vaop/ncurrent/extref/nnano.2009.235-s1.pdf
Very poor reporting here, and not juts from slashdot alone this time.
Two of the links talk about research done in the UK researchers, the third link about that it is done in Israel. One article mentions 62 volunteers, another 94. While it seems they are talking about the same research project - none is referring to the other though.
And of course that 83% number. That means 17% false negatives for cancer patients? How is the false positive rate then for non-patients? In other words: how useful is this test in real life? If healthy people still get a say 70% positive rate it's quite useless I'd say.
Interesting and all that a breath analyses could indicate the presence of cancer but the articles as linked do not make me believe it really exists in a working sense or that it is actually useful at this time. The articles linked at least are too light on detail, and even state facts differently. Unless there are two research groups working on the same thing together (one in UK, the other in Israel), but then why don't the articles refer to this fact?
Hooray, they are only 17% likely to get a false negative on a sick person, and something less than 83% (82%? 50%?) likely to get a false positive on someone healthy.
Combining that with the statistical problem of detecting a rare disease, that's not really useful as the number of true positives vanishes against that of false positives. (Even assuming their results aren't down to a correlation like smoking.)
If they weren't in it for the money. This would never have been made!
Since when did research/production/innovation with the goal of making money become a bad thing? It's like it's become a taboo.. making money, it's for the exchange of goods and services!
Pay them in jelly-beans! everyone loves jelly-beans! awww look! they're doing it for jellllyyy beeaaanns
P.R. Alert: This Slashdot story is a public relations release. The misleading Slashdot summary says, "Other sources have picked up the story...". In reality, they are inserting press releases everywhere they can, and the kind of work being done is not new.
... believes that the breath test will provide a more convenient and rapid method for diagnosing serious diseases than blood or urine analysis, and will require minimal medical intervention."
It was proven long ago that dogs can smell chemicals associated with cancer. For example, see this 2006 article in National Geographic News, Dogs Smell Cancer in Patients' Breath, Study Shows. That's part of what started the present interest in making a machine to detect cancer.
This February 2007 article is more interesting: Compact lung-cancer breath test may be possible. Quote: "The test uses 36 chemical dots that react to telltale compounds in a person's breath. The dots change colour when exposed to compounds that signify the presence of lung cancer."
This February 2007 article gives more information about how it is done: US Scientists Prototype Breath Test For Lung Cancer
Even Oprah's magazine had article in June 2009 about dogs sniffing cancer and making machines to imitate dogs: Sniffing Out Cancer. Quote: "The researchers are collaborating with scientists at the University of Maine, who are trying to mimic the dogs' cancer-sniffing abilities with laboratory machines." Another quote: "So far, the Pine Street Foundation dogs have done 25,000 scent trials for ovarian cancer."
Slashdot: Not quite as current as Oprah? Old news for nerds who were playing video games and wouldn't know the difference?
Many researchers are doing similar work. For example, see the February 2008 article, The Cancer Breathalyzer. Quote: "Dr Yousef
Other researchers are studying the possibility of using blood tests to detect cancer. See the December 2007 article, Study points to possibility of blood test to detect lung cancer.
Here is a November 2005 research paper that surveys some of the issues of early detection of cancer: The Progress and Promise of Molecular Imaging Probes in Oncologic Drug Development.