Dogs Smell Cancer in Patients' Breath, Study Shows

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Dogs Smell Cancer in Patients' Breath, Study Shows

Stefan Lovgren

for National Geographic News

January 12, 2006

 

Dogs can detect if someone has cancer just by sniffing the person's breath, a

new study shows.

 

Ordinary household dogs with only a few weeks of basic " puppy training " learned

to accurately distinguish between breath samples of lung- and breast-cancer

patients and healthy subjects.

 

" Our study provides compelling evidence that cancers hidden beneath the skin can

be detected simply by [dogs] examining the odors of a person's breath, " said

Michael McCulloch, who led the research.

 

Early detection of cancers greatly improves a patient's survival chances, and

researchers hope that man's best friend, the dog, can become an important tool

in early screening.

 

The new study, slated to appear in the March issue of the journal Integrative

Cancer Therapies, was conducted by the Pine Street Foundation, a cancer research

organization in San Anselmo, California.

 

Biochemical Markers

 

Dogs can identify chemical traces in the range of parts per trillion. Previous

studies have confirmed the ability of trained dogs to detect skin-cancer

melanomas by sniffing skin lesions.

 

Also, some researchers hope to prove dogs can detect prostate cancer by smelling

patients' urine.

 

" Canine scent detection of cancer was something that was anecdotally discussed

for decades, but we felt it was appropriate to design a rigorous study that

seriously investigated this topic to better evaluate its effectiveness, " said

Nicholas Broffman, executive director of the Pine Street Foundation.

 

Lung- and breast-cancer patients are known to exhale patterns of biochemical

markers in their breath.

 

" Cancer cells emit different metabolic waste products than normal cells, "

Broffman said. " The differences between these metabolic products are so great

that they can be detected by a dog's keen sense of smell, even in the early

stages of disease. "

 

The researchers used a food reward-based method to train five ordinary household

dogs.

 

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.

 

Different Wiring

 

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. "

 

http://news.nationalgeographic.com/news/2006/01/0112_060112_dog_cancer.html