LONDON - German scientists experimenting with sniffer dogs have found they can accurately detect lung cancer by smelling breath samples.

In a study carried out by researchers from Schillerhoehe Hospital in Germany, the dogs were able to correctly detect lung tumours in 71 percent of patients, suggesting a similar technique could be used for early detection in future.

"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," said Thorsten Walles, who led the study and published its findings in the European Respiratory Journal on Thursday.

Lung cancer, mostly linked to smoking, is the second most common form of cancer in men and women across Europe and causes more than 340,000 deaths per year. It is also the most common cause of death from cancer worldwide.  

The disease is notoriously hard to detect in its early stages and scientists have been working on using breath tests for possible future screening programmes. The sniffing method relies on identifying so-called volatile organic compounds (VOCs) that are linked to the presence of cancer.  

The researchers explained that although many different possible breath test techniques have been tried, they are very difficult develop for use in practice in clinics because patients are not allowed to smoke or eat before the test, sample analysis can take a long time and there is also a high risk of interference. Because of these reasons, no lung cancer-specific VOCs have yet been identified.

In this study the researchers worked specially-trained dogs and with 220 volunteers, including some lung cancer patients, some patients with chronic obstructive pulmonary disease (COPD) patients and some with no lung health problems.  

The results show the dogs successfully identified 71 samples with lung cancer out of a possible 100, and correctly detected 372 samples that did not have lung cancer out of a possible 400.

The animals were also able to detect lung cancer independently from COPD and tobacco smoke.

Walles said their results confirm that there is a reliable and stable "marker" for lung cancer in the breath, but there is still a lot of work to do to find out exactly what that is.

"This is a big step forward...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."