Dogs in Training to Sniff Out Cancer

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Dogs in Training to Sniff Out Cancer

 

John Roach

for National Geographic News

August 20, 2004

 

Some people say that old dogs can't be taught new

tricks. But don't tell that to Larry Myers.

 

A professor of veterinary medicine at Alabama's Auburn

University, Myers has trained unwanted dogs to detect

everything from drugs and bombs to off-flavor catfish

and agricultural pests.

 

Myers says that, with proper training, just about any

dog can learn to detect a unique scent—even the odor

of certain cancers

 

" Some dogs are more conditioned to training than

others. But that's differences between individuals

[not breeds], " he said. Myers usually works with dogs

rescued from the pound.

 

James Walker, director of the Sensory Research

Institute at Florida State University in Tallahassee,

says canines' sense of smell is generally 10,000 to

100,000 times superior to that of humans.

 

Walker plans to train dogs to detect prostate cancer

in human urine later this year.

 

It's uncertain why dogs are so much better at smelling

than humans are. But Walker says it is probably

related to how dogs are " wired. "

 

Recent research shows that dogs have a greater variety

of smelling receptors in their noses. They also have a

greater convergence of neurons from the nose to the

brain than humans do.

 

" It is clear that the dog has a much greater

proportion of its brain devoted to smell than is the

case with humans, " Walker added.

 

Myers, the veterinary professor, notes that, in

general terms, dogs and humans are similarly wired for

smelling. But he adds that more research is needed to

determine the subtle differences between man and mutt,

including the mucus that overlies our different

smelling receptors and the molecules that make up

those receptors.

 

Cancer Detection

 

Cancer represents the frontier of dog-detection

research. Anecdotal evidence suggests it may be

possible for dogs to sniff out certain malignancies.

But the science still lags, according to Myers. " We

hope we can. We think we can. But we don't know that

we can. "

 

Later this year Walker and his colleague and wife,

Dianne, hope to show that canine cancer detection can

be done.

 

The husband-and-wife team intend to use a special

technique as they study the ability of dogs to detect

prostate cancer in human urine samples.

 

The training program uses a chemical stimulus, n-amyl

acetate, which smells like bananas.

 

Working with the bananalike scent, which the dogs

already recognize, will allow the researchers to prove

their dogs are well-trained. Put simply, the duo will

steadily lower the concentration of the

banana-smelling chemical in test samples, then slowly

introduce urine samples with and without cancer cells

into the training regimen.

 

" If the dog goes from getting it right about half the

time to doing it much better than that, or even

showing perfect performance—let's say it takes two

months to learn—what that would show is the dog is

learning to categorize the urine samples into two

classes: normal versus cancer, " Walker said.

 

At that point, the researchers would phase out n-amyl

acetate altogether and only test dogs on urine

samples.

 

Since the urine samples will have already been

screened by doctors, successfully trained dogs should

only be as good as their medically trained human

counterparts.

 

The final step in the dogs' training will require

several years of rigorous analysis: Canines must be

tested on unscreened urine. Researchers would record

the dogs' analysis and track human patients to

determine if the dogs are able to diagnose cancer any

earlier than conventional medical techniques allow.

 

Walker cautions that the work is preliminary. He adds

that it will be at least another five years before

dogs, or any canine-inspired technology, greet people

who visit their doctor's office for cancer screening.