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 tumors 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," says Thorsten Walles, who led the study and published its findings in the European Respiratory Journal.

Lung cancer, mostly linked to smoking, is 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 programs. The sniffing method relies on identifying so-called volatile organic compounds (VOCs) that are linked to the presence of cancer.

Walles says 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."