Researchers from Schillerhöhe Hospital in Germany have published a study in the European Respiratory Journal that shows that dogs can detect lung cancer by sniffing human breath.
Two German shepherds, an Australian shepherd and a Labrador retriever smelled test tubes containing breath samples from 220 patients, only some of whom had lung cancer. The researchers trained the dogs to lie down in front of the test tubes where they smelled lung cancer and touch the vial with their noses, according to CNN.
The dogs sniffed the presence of lung cancer in 71% of samples from lung cancer patients and had a low rate of false positives, correctly identifying 93% of the cancer-free samples, Reuters reports.
According to Time Magazine:
That's better than the imaging tests that most physicians currently use to detect lung cancer. WebMD reports that in a recent study, longtime smokers who went in for annual CT scans of their lungs cut their risk of dying from lung cancer by only 20%.
“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,” lead researcher Thorsten Walles said in a statement.
In other studies, dogs have sniffed out breast cancer, bowel cancer, colon cancer, and type 1 diabetes with varying degrees of accuracy.
“This is probably the most sophisticated study I've seen on this topic,” Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society, told CNN. “More and more studies are reinforcing the possibility that this is very real,” he says.
There is still a lot of work to be done before smell tests can be developed to detect cancers, researchers said. “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,” Walles said. “It is unfortunate that dogs cannot communicate the biochemistry of the scent of cancer!”