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."
Re:Early detection doesn't always improve outcomes (Score:3, Informative)
Incidentally, one thing I learned from the experience is that although a fair percentage of older men die with prostate cancer, very few die of it because it generally doesn't start until fairly late in life and grows very slowly. Much of the time, about all that's done is keep an eye on it to see if it's getting bad enough to need treatment.
Re:Sensitivity and specificity? (Score:4, Informative)
Confirmed:
It's 86 percent accuracy:
http://www.google.com/hostednews/afp/article/ALeqM5gD0oDWeDtMfAYl0C5bvx6Yyd78Yg [google.com]
Re:Makes sense (Score:3, Informative)
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 [nature.com]
P.R. Alert. Misleading Slashdot summary. (Score:5, Informative)
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 [nationalgeographic.com]. 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 [newscientist.com]. 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 [medicalnewstoday.com]
Even Oprah's magazine had article in June 2009 about dogs sniffing cancer and making machines to imitate dogs: Sniffing Out Cancer [oprah.com]. 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 [medgadget.com]. 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 [physorg.com].
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 [aacrjournals.org].
Re:Sensitivity and specificity? (Score:5, Informative)
That's not how it works. Assuming 83% is the accuracy for both positives and negatives, and given a group of 100 people, 10 of whom have lung cancer, we would expect on average:
2 patients with cancer will not be detected.
17 cancer-free patients will be told they may have cancer.
If our patients have no increased risk for cancer, then our group of 17 false-positives are suddenly scared into receiving further (possibly expensive) further testing. Our two patients whose cancer was not detected ignore futher testing until it is too late.
Basically, this technique is mostly useless for general screening. Of course, widespread screening generally is a bad idea, due to false positives, so the best bet is always to stick with those with higher risks only. I could see this method gaining use in developing nations where an expensive test is not possible, as the false-negative rate is still smaller than the current rate of undiagnosed cancer. However, dealing with the false-positives is still a bitch.
Re:Oscar (cat) (Score:3, Informative)
Re:Early detection doesn't always improve outcomes (Score:3, Informative)
How did the parent get modded as insightful? Let's try this again. Comparing almost always fatal lung cancer (from TFA) affecting a variety of age groups to slow-moving often 'clinically irrelevant' prostate cancer (not from TFA) whose onset affects primarily the elderly is both Troll and Offtopic.
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Primary lung cancers themselves most commonly metastasize to the adrenal glands, liver, brain, and bone. Secondary lung cancers can be indicative of other cancers whose prognosis is also dependent upon the earliest possible detection. Someone explain to this onc that catching these lung cancers before they metastasize is ALMOST ALWAYS worth the treatment risk. Almost all factors (excepting cell type) that affect prognosis in non-small cell lung cancer are factors that can be enhanced by early detection: presence or absence of pulmonary symptoms, tumor size, metastases to lymph nodes, and vascular invasion.
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Comparing lung cancer to prostate cancer in this way is medically irrelevant and offtopic.