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.

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