Cancer Research Lab

Using exhaled breath, a colorimetric chemical sensory array (ChemSensing, Champagne, Illinois) can distinguish between patients with lung cancer and healthy subjects, according to research published ahead of print in Thorax.

Cancer cells undergo metabolic changes that alter the production and processing of volatile organic compounds, explain lead author Dr. Peter J. Mazzone and his colleagues at the Cleveland Clinic in Ohio.

Previously, these gaseous variations required gas chromatography and mass spectroscopy, which are expensive and require expert interpretation, Dr. Mazzone said.

ChemSensing has designed systems with a customized colorimetric sensor array that uses “metalloporphyrins that hold metal ions tightly, but with open sites,” the company explains on its web site. “When exposed to volatile organic compounds, the metalloporphyrins produce measurable color changes.”

ChemSensing’s system was first developed to identify and measure levels of potentially deadly gas exposures, as might be encountered in the case of a bioterrorist attack or a major industrial accident. It has also been used to detect bacterial food spoilage.

The system used by the Cleveland Clinic’s scientists contained 36 “chemically sensate spots,” each with different sensitivities to volatile organic compounds. The authors “chose a broadly sensitive system, as the identity of the key volatiles that make the breath of patients with lung cancer unique has not been clearly established.”

For their “proof of principle study,” the team enrolled 49 patients with non-small cell lung cancer, 73 with nonmalignant pulmonary diseases, and 21 healthy control subjects.

To obtain samples, subjects performed tidal breathing of room air for 12 minutes, inhaling through their nose and exhaling through their mouth into the breath collection device. The exhaled air was drawn over the sensor array by a pump. A scanner was then used to quantify color changes at each spot.

A prediction model was constructed using results from 70% of subjects, which the researchers then verified by testing the remaining 30% of subjects.

Results showed that the assay was 73.3% sensitive for lung cancer, with 72.4% specificity. Results were not affected by subjects’ gender, age, or smoking history. The system was able to detect cancers of any tumor size, type, or cancer stage.

“These results suggest a lot of promise for developing this type of test for detecting lung cancer,” Dr. Mazzone said. However, “what is needed before it can be applied in clinical settings,” is to identify what volatile organic compounds are involved, and “to figure out what makes the cancer patient’s breath different.”

“But I want to be as honest and up-front as possible,” Dr. Mazzone said. “I do not know if this type of device will ever develop into something clinically useful. But what we’ve seen holds out enough promise that we want to continue to pursue this line of study.”