A Breathalyzer For Cancer 123
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."
False positives? (Score:2, Insightful)
Early detection doesn't always improve outcomes (Score:5, Insightful)
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.
Re:Sensitivity and specificity? (Score:4, Insightful)
Re:Makes sense (Score:3, Insightful)
Re:Sensitivity and specificity? (Score:4, Insightful)
Re:Makes sense (Score:5, Insightful)
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.
Living causes cancer. (Score:2, Insightful)
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.
Re:Sensitivity and specificity? (Score:3, Insightful)
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.
Re:Painfully fucking stupid and ten years out of d (Score:3, Insightful)
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."
Re:Early detection doesn't always improve outcomes (Score:4, Insightful)
It depends on how you value various things. Detecting a lot of people who would not have died anyway in Phase 1 will raise your overall survival rates (those people will still live), but may make a whole lot of people's lives shittier. Is removing an X% change you'd have died worth a Y% chance that you unnecessarily made your life shitty for years? Depends on X, Y, and your preferences.
Bad test. (Score:3, Insightful)
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....
Re:Bad test. (Score:4, Insightful)
"Just recently?" That's been a standard example in introductory statistics classes for many decades.
Very poor reporting (Score:3, Insightful)
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?
Less than 83%? (Score:3, Insightful)
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.)
Re:Makes sense (Score:5, Insightful)
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
Re:Sensitivity and specificity? (Score:5, Insightful)
I would run whichever test had the highest profit margin.
Re:Bad test. (Score:3, Insightful)
There's no such thing as a 'bad test' that has a high rate of accuracy, there are only people who are using the test wrong.
With 86% accuracy, you can't rely on this test... But if it comes up positive, then you know you had better check them with a better, more expensive, less fallible test.
If this test were cheap enough to use it on every patient that came in for anything, it would be a -huge- boon to society. If it cost 10x what a checkup costs, it'd be utterly useless.
Re:Bad test. (Score:3, Insightful)
In my example, in the population 99.9% of the people don't have the disease. In those that tested positive, 90% still don't have the disease. That's with a 99% accurate test.
It's very difficult to effectively use a test that has an error rate of on the order of 17%. Or to be more accurate: A false negative rate of about 17%, and a false positive rate of "less than 83""....
But yes, you're right. It only becomes bad when people use the test wrong.
The research I don't remember the reference to however showed that in practise, submitting those 9990 healthy people from my example to further tests was not beneficial to the group as a whole.....
Part of the problem is unsolvable: Doctors aren't statistics-professors. So even though they are well educated they still fall for some of the statistical pitfalls that exist. And with these huge error rates the effects of those pitfalls are big, and the temptation to fall for them large.
Re:Living causes cancer. (Score:3, Insightful)
After a while the immune system may have to kill nearly every cell to do that, including many of its own cells. It'll be a bit like removing all the rust from an old car that's already mostly rust
My guess is after a while of aging it's hard for the body to figure out what is a good cell - since the cells would have drifted "apart" from each other and the "ideal" - one skill cell would be not quite the same as another skin cell (just look at old skin and a baby's skin), and the immune system can't go around killing all the inferior clones since the body has stopped being able to make "perfect" clones.
That's probably a reason why you have reproduction - out of very many cells you start all over again with two cells that are hopefully good enough.
Genetic drift for bacteria and other unicellular stuff is nothing since they aren't as dependent on the rest of their clones behaving "properly".
If you have tech to kill all bad cell clones, you probably can't use it on Chimeras, and people that have transplants from other people/creatures. The bacteria in your body might also have "issues" with that tech
We may still be able to do better than 140ish years, since other animals apparently can manage that.