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."
"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.
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.
Yeah... that was my first reaction. With a false-positive rate that high, this is useless as a diagnostic tool.
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.
It depends on how quick and cheap this test is. If it's really cheap, then it would be useful in validating more accurate (and inherently more expensive) tests that would be used for initial detection or risk assessment. As a hospital manager would you rather run 83 cheap tests and 17 expensive ones to confirm or 100 expensive tests; again it depends on the cost. On the other hand, I'd be more worried about the false negatives. Not being diagnosed with cancer, when you have it, and getting early treatment is much worse than getting an extra test, at least from the patient's perspective.
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.
I think that the article is trying to say that "fewer than 83 percent" means that the remaining percentage is the "fewer", AKA the 17 percent.
I'm hopeful that it's just a case of poor wording, as it wouldn't be an effective test or really news worthy other than a study if it got 83% false positives.
Making the actual testing device seems to give credit to the idea that it is a mis-statement of the results.
) Human Kind Vs Human Creation
) It'd be interesting to see how many humans would survive to serve us.
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."
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....
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
I would run whichever test had the highest profit margin.