Last year we reported in the development of a cancer-detecting electronic nose inspired by dogs' ability to literally sniff out different types of ovarian cancer. Now a new study has found that sniffer dogs' abilities extend to reliably detecting lung cancer. The researchers say the results of the study confirm that there is a stable marker for lung cancer, which offers the possibility that a "breath test" for the early detection of lung cancer could be developed.

According to the European Lung Foundation, lung cancer is the second most frequent form of cancer in men and women across Europe and accounts for over 340,000 deaths each year. Although the chances of survival are relatively high when detected early, because many of the symptoms of lung cancer are nonspecific it is often not diagnosed before the cancer has spread and early detection is often only by chance.

To provide a simple way to detect lung cancer in its early stages, researchers have been working to identify volatile organic compounds (VOCs) that are linked to the presence of cancer. In an attempt to confirm the presence of such identifying compounds, researchers from Schillerhoehe Hospital in Germany conducted tests using exhaled breath specimens provided by 220 volunteers, including lung cancer patients, chronic obstructive pulmonary disease (COPD) patients and healthy patients.

Specially trained sniffer dogs successfully identified 71 samples of lung cancer out of a possible 100 and correctly detected 372 samples that didn't have lung cancer out of a possible 400. Although it isn't known which specific chemical the dogs are responding to, the researchers say the results confirm there is indeed a stable marker for lung cancer that is independent of COPD and is detectable in the presence of tobacco smoke, food odors and drugs.

"In the breath of patients with lung cancer, there are likely to be different chemicals to normal breath samples and the dogs' keen sense of smell can detect this difference at an early stage of the disease," says author of the study, Thorsten Walles. "Our results confirm the presence of a stable marker for lung cancer. This is a big step forward in the diagnosis of lung cancer, but we still need to precisely identify the compounds observed in the exhaled breath of patients. It is unfortunate that dogs cannot communicate the biochemistry of the scent of cancer!"

While it isn't feasible to use sniffer dogs in clinics, the results of the study offer hope that once the chemical the dogs are responding to is identified, an electronic nose could be developed to literally sniff out lung cancer in a patient's breath.

The new study is published in the European Respiratory Journal.