— The sensor array used in this study consists of 36 chemically-sensitive dots on a disposable cartridge (Image: Thorax)
A simple breath test can sometimes detect lung cancer in patients even those in the early stages of the disease US researchers reported on Sunday.
The researchers developed a compact device that correctly diagnosed three-quarters of lung cancer patients in trials involving 122 people with different types of respiratory disease. The sample included 49 people with lung cancer and 21 healthy controls. However, the test also wrongly diagnosed many people with lung cancer when they did not have the disease.
The researchers say a more accurate test may be possible in principle. "The unique chemical signature of the breath of patients with lung cancer can be detected with moderate accuracy by a [colour-producing] sensor array," the researchers write.
Catching lung cancer early, when it is still treatable, could save tens of thousands of lives per year in the US alone. It is the most common form of malignant cancer and also kills more people than any other cancer, in part because it is not usually detected until it has spread.
Researchers know that tumour cells produce different compounds compared to normal cells. These volatile organic compounds should be detectable, especially in lung cancer, because people exhale air that is directly affected by the cells.
"The pattern of volatile organic compounds in the exhaled breath of patients with lung cancer may be unique," Peter Mazzone at the Cleveland Clinic in Ohio, US, and colleagues write in their report.
Tests involving mass spectrometers show that such a test should be possible. But such equipment is large and expensive so could not be made available to most patients.
Mazzone's team worked with the company ChemSensing of Champaign, Illinois, US, to develop a compact test that could ultimately be used to make a portable device. 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.
They incorporated it into a device and had volunteers breathe through it for 12 minutes. It correctly identified 73% of patients with lung cancer, and it correctly cleared healthy subjects of lung cancer 72% 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 concludes.
So far, the most accurate way to detect cancer using breath has been with dogs. In January 2006, researchers found that dogs could be trained to smell cancer on the breath of patients with 99% accuracy (see Dogs as good as screening for cancer detection).
A type of X-ray called "spiral computed tomography" can find lung cancer early, but is also expensive and sometimes pinpoints non-cancerous lesions that are expensive and risky to test.
Last year in the US, lung cancer was diagnosed in over 174,000 people, and killed over 160,000. It kills approximately 1.3 million people globally every year.
Journal reference: Thorax (DOI: 10.1136/thx.2006.072892)