June 11, 2002 -- Dogs could soon become man's best friend when it comes to detecting prostate cancer if new research plans are successful.
Researchers at Cambridge University Veterinary School in England are awaiting funding to test the viability of what they call "dognoseis" — detecting the traces of prostate cancer by training dogs to smell signatures of the disease in urine samples.
The veterinary researchers hope that dogs might someday play a role in screening patients for early signs of prostate cancer, although some medical professionals remain skeptical.
"If the dogs can be trained to a high level of accuracy, which we think can be done, then many people can be screened a lot faster and a lot earlier," said Charlie Clarricoates, the lead dog trainer for the project.
Past cases led the Cambridge researchers to think dogs would be up to the task. As detailed in the British medical journal The Lancet in 1989, a border collie-Doberman mix belonging to a British woman repeatedly sniffed a mole on its owner's thigh and once even tried to bite it off. The constant attention prompted the woman to have the lesion examined and she learned it was a malignant melanoma.
"The dog may have saved her life by forcing her to seek medical advice while the mole was still at a thin stage," wrote Hywell Williams and Andrew Pembroke, surgeons at the dermatology department at King's College Hospital in London, in a letter to The Lancet.
In another case, a pet Labrador named Parker repeatedly pushed his nose against his 66-year-old owner's leg, sniffing a lesion through the owner's pants. When the man had the lesion examined, he learned it was a basal cell carcinoma, a form of skin cancer, and had it removed.
Neither dogs showed any interest in their owners' lesions after they were treated.
After seeing the Lancet report, Armand Cognetta, a dermatologist at a clinic in Tallahassee, Fla., began collaborating with a police dog handler to train dogs to locate and retrieve tissue samples of melanoma that had been removed and stored in bottles. When the dog, George, proved 100 percent successful in detecting melanoma samples in tests, Cognetta had it smell suspect areas on his patients' skin. He reported the dog was nearly 100 percent successful in detecting cancerous skin lesions in patients.
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While researchers don't know exactly what dogs might smell in the urine of prostate cancer patients, they feel confident the animals will find some unique scent and can be trained to signal for them.
To prepare for the tests, Clarricoates has trained two Labrador retrievers and one German shepherd to run their noses along compartments in a metal trough on the floor. He explains once the project is under way, each compartment will contain the urine samples of men who have prostate cancer and those who do not.
Clarricoates plans to train the dogs to lie down when they smell the urine samples from prostate cancer patients. To reinforce the behavior, he'll use the same tools he uses when training dogs to detect drugs: a tossed tennis ball or a juicy meat treat.
"I know they'll be able to do it. The challenge is they'll have to be 100 percent accurate," he said.
Paul Waggoner, director of the canine program at the Institute for Biological Detection Systems at Auburn University in Alabama, explains dogs are born equipped with one of nature's best smelling tools.
Humans and dogs smell odors using a membrane called the olfactory epithelium. Lining the membrane are receptors topped with tiny hairs that pick up chemicals and transmit the sense of odor by sending electrical chemicals to the brain. While people have about 40 million olfactory receptors, dogs have about 2 billion.
"Depending on what odors there are, dogs can smell from 1,000 to 100,000 times better than people," said Waggoner. "They are very much odor-guided."
Since dogs (particularly Labrador retrievers and German shepherds) have been bred to respond well to human interaction, Waggoner says it's fairly simple to train the animals to signal when they've caught a scent. He estimates it takes about 70 to 100 repetitions over two to three weeks to train a dog to signal an odor.
Clarricoates says he hopes to train his dogs for six months to ensure they become extremely accurate in detecting signs of prostate cancer. But medical professionals say it may be difficult to reach the level of accuracy needed to win government approval for the tests.
"A screening test is not something you can do lightly," said John Voss, an associate professor of clinical internal medicine at University of Virginia Health Systems in Charlottesville, Va. "A positive test leads to a cascade of expensive, intrusive examinations. So you want to be really sure the screening test is a good one."