Dogs
in Training to Sniff Out Cancer John Roach 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.
for National Geographic News
August 20, 2004