Your breath can tell a lot more about you than whether you brushed your teeth this morning or have been drinking alcohol. Researchers at the Cleveland Clinic have developed a sensor that can identify telltale chemicals in the breath of people with lung cancer. Lung cancer is difficult to detect in its early stages and difficult to treat when diagnosed in its late stages. Researchers hope that with further development, the breath sensor, an array of chemically sensitive dye spots, will help catch the disease earlier.

Lung cancer causes 160,000 deaths a year in the United States--more than any other cancer. Current diagnostic techniques including CT scans and needle biopsies are invasive and expensive and have a high risk of complications, says Peter Mazzone, a pulmonologist at the Cleveland Clinic. "We need an easy-to-use test for finding early-stage lung cancer," he says.

Some of the products of metabolism, called volatile organic compounds, are carried in the breath and can serve as biomarkers. Cancer cells make different groups of these volatile compounds than normal cells do. Researchers have known since the mid-eighties that these differences can be detected on lung-cancer patients' breath using a combination of gas chromoAtography and mass spectrometry. But Mazzone says applying these sophisticated analytical techniques to cancer diagnosis is expensive--it requires trained technicians and large machines--and they have not proved accurate enough for clinical use.

The Cleveland lung-cancer sensor is a disposable piece of paper called a colorimetric array. The paper has 36 chemically sensitive dye spots that change color when they interact with compounds in the breath. Changes in color are read by a flatbed scanner, which sends the images to a computer for analysis.

In a proof-of-principle study, Cleveland Clinic researchers analyzed the breath of 143 patients, some healthy, some known to have lung cancer, and some with other lung diseases. Patients breathed into a machine that kept their exhalations at body temperature and circulated them over the sensing array. The doctors modeled the patterns of color changes in the sensor array characteristic of lung cancer, then used the model to try to detect lung cancer in the remaining patients.