A new study adds to the body of research suggesting that "man’s best friend" may actually be able to smell cancer.

Researchers in Germany found that dogs were able to pick up on the scent of organic compounds linked to the presence of lung cancer in the human body, and that their keen sense of smell may be useful for the early detection of the disease.

Four family dogs – two German shepherds, one Australian shepherd and one Labrador retriever – smelled test tubes containing breath samples of 220 patients, both those with lung cancer and those without it. The dogs were trained to lie down in front of the test tubes where they smelled lung cancer and touch the vial with their noses. According to the study, the dogs successfully identified lung cancer in 71 out of 100 patients with the disease.

And that’s not all. Researchers also tested patients with chronic obstructive pulmonary disease. “COPD is quite common in patients with lung cancer and we were not sure if the dogs could tell the difference between both diseases,” explains Enole Boedeker, an author on the study who practices general thoracic surgery in Stuttgart, Germany. “The dogs could recognize the cancer sample as easily as between the breath samples of the healthy study participants,” Boedeker says. The study is published in the European Respiratory Journal.

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This isn’t the first study to use dogs’ heightened sense of smell to identify disease in humans. Over the years researchers have theorized that cancer may actually have a detectable scent - cancer cells may produce chemical compounds that circulate throughout the body and can be breathed out of the lungs in a gaseous form. The use of canine scent to detect these compounds has shown promise in sniffing out breast cancer, bowel cancer, colon cancer, COPD and lung cancer, and even type 1 diabetes.

“This is probably the most sophisticated study I've seen on this topic,” says Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. Lichtenfeld has been following research on sniffer dogs and blogged about the topic for ACS. “More and more studies are reinforcing the possibility that this is very real,” he says.

But don’t expect to see Fido in the office the next time you visit the doctor; the future clinical implications remain unknown.

“We've seen this happen enough to suggest there are compounds in the breath of patients with cancer that could provide an early warning about he presence of cancer in the body, but we still do not know exactly what those compounds are,” Lichtenfeld says. “We can’t pick out what the dogs smell.”

Researchers say sniffer dogs are a promising “detection device,” but more studies are needed to help identify the specific detectable markers in order to create screening methods.

“Unfortunately,” the study authors conclude, “dogs cannot communicate the biochemistry of the scent of cancer.”