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WASHINGTON - A simple breath test can sometimes detect lung cancer in patients even in the early stages of the disease, proving in principle that the idea might work, United States researchers reported today.
The breath test device, the size of a coin, detected three-quarters of the people with lung cancer who the researchers tested. But it had too many false positives -- meaning it indicated lung cancer in people who did not have it.
Nonetheless, researchers said their study, published in the journal Thorax, showed that such a test is possible in principle if someone developed a more accurate version.
"The unique chemical signature of the breath of patients with lung cancer can be detected with moderate accuracy by a colorimetric sensor array," the researchers wrote.
Catching lung cancer early, when it is still treatable, could save tens of thousands of lives a year in the United States alone.
It is the most common form of malignant cancer and also kills the most people, in part because it is not usually detected until it has spread.
Researchers know that tumour cells produce different compounds than normal cells.
These volatile organic compounds should be detectable, especially in lung cancer, because people exhale air that is affected by the cells.
"The pattern of volatile organic compounds in the exhaled breath of patients with lung cancer may be unique," Dr Peter Mazzone of the The Cleveland Clinic in Ohio and colleagues wrote in their report.
Tests using large machines called mass spectrometers show that such a test should be possible but those tests are very expensive and not viable for the average patient.
Mazzone's team worked with privately owned ChemSensing of Champaign, Illinois, to develop a small test that could be put into a portable device.
They made one with 36 little spots of compounds designed to be triggered by some of these compounds. These dots would change colour if they interacted with the compounds.
They put it into a device that people could breathe into and then recruited 143 people -- some with various types of lung cancer, some with other lung diseases such as emphysema and some healthy.
They had them breathe into the device for 12 minutes.
It found 73 per cent of the patients with lung cancer, and it correctly cleared patients of lung cancer 72 per cent of the time.
"Ultimately, this line of investigation could lead to an inexpensive, non-invasive screening or diagnostic test for lung cancer," Mazzone's team concluded.
So far, the most accurate detector of cancer has been dogs. In 2006, researchers found dogs could be trained to smell cancer on the breath of patients with 99 per cent accuracy.
A type of X-ray called spiral computed tomography or CT can find lung cancer early, but it is expensive and also finds non-cancerous lesions that are expensive and risky to test.
Last year, lung cancer was diagnosed in more than 174,000 Americans and killed more than 160,000. It kills 1.3 million people globally every year.
- REUTERS
