Encountering breath samples captured in tubes, the dogs gave a positive identification of a cancer patient by sitting or lying down in front of a test station.
By scent alone, the canines identified 55 lung and 31 breast cancer patients from those of 83 healthy humans.
The results of the study showed that the dogs could detect breast cancer and lung cancer between 88 and 97 percent of the time.
The high degree of accuracy persisted even after results were adjusted to take into account whether the lung cancer patients were currently smokers.
"It did not seem to matter which dog it was or which stage cancer it was, in terms of our results," Broffman said.
According to James Walker, director of the Sensory Research Institute at Florida State University in Tallahassee, canines' sense of smell is generally 10,000 to 100,000 times superior to that of humans.
It is unclear what exactly makes dogs such good smellers, though much more of the dog brain is devoted to smell than it is in humans. Canines also have a greater convergence of neurons from the nose to the brain than humans do.
"The dog's brain and nose hardware is currently the most sophisticated odor detection device on the planet," McCulloch, the study leader, said. "Technology now has to rise to meet that challenge."
Researchers envision that dogs could be used in doctors' offices for preliminary cancer detection.
"There are lots of experimental treatments," Walker said. "This could be an experimental diagnostic tool for a while, and one that is impossible to hurt anyone with or to mess up their diagnosis with."
Broffman, the Pine Street director, hopes to build on the current study to explore the development of an "electronic nose."
"Such technology would attempt to achieve the precision of the dog's nose," he said. "Such technology would also be more likely to appear in your doctor's office."
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