Last March, soon after Debbie Marvit-McGlothlin learned she was pregnant, her dog Autumn started sniffing a tiny mole on the back of her leg.

	Tony Tye, Post-Gazette Debbie Marvit-McGlothlin's dog Autumn licked and bit at a mole on her owner's leg that, upon biopsy, revealed melanoma. Click photo for larger image.

"Then she became more aggressive," Marvit-McGlothlin said of the 2-year-old shepherd-hound mix. "She'd lick it and lick it for maybe an hour. I just ignored it. Then I'd walk down steps and she'd be biting it or scratching it."

In June, Marvit-McGlothlin, 28, of Troy Hill brought the mole and her dog's behavior to the attention of her obstetrician, who took the mole off and had it biopsied.

The result: The mole was melanoma, the most severe type of skin cancer that kills 8,000 people a year in the United States.

Two weeks later, doctors took out more skin around the mole for further testing and concluded that all the melanoma had been removed before it had spread to her lymph nodes. So, apparently, did Autumn.

"She hasn't touched it since it's been gone," Marvit-McGlothlin said. "I had a big dressing for three weeks."

A fluke?

Similar anecdotal reports and a recent, ground-breaking scientific study on the cancer-sniffing ability of dogs suggest no.

Dr. Hywel Williams and Dr. Andrew Pembroke, of the Dermatology Department at King's College Hospital in London, described a case in a letter to The Lancet in 1989 in which a dog kept sniffing a lesion that proved to be a malignant melanoma.

In the latest study appearing in the British Medical Journal, involved training six dogs previously unschooled in scenting to identify people with bladder cancer on the basis of urine odor.

The result: Collectively, the dogs correctly selected urine samples from patients with bladder cancer on 22 of 54 occasions, or 41 percent of the time, compared to 14 percent by chance alone. On each of the 54 tests, the dogs had to select one sample from among seven.

"We had a feeling as we went through training that the dogs were learning to do this task, so when we exposed them to the test, it was not a complete surprise they were able to do it," said Dr. Carolyn M. Willis, a key member of the study team who is director of academic research at Amersham Hospital in England.

"We made the job very, very difficult because we had such a wide range of controls [healthy and unhealthy men and women with no bladder malignancy]."

Willis was not surprised to hear of Marvit-McGlothlin's experience with Autumn.

"Since then, I've been contacted by at least 10 people with similar stories, dogs sniffing cancers, some of them internal," Willis said. "They're not isolated events. There seem to be more and more people coming forward.

"The main thing to point out is our study doesn't prove the stories are correct, but it does provide some scientific basis for them. ... The study shows there might well be something that lies behind them."

Dr. John Kirkwood, director of the melanoma and skin cancer program center of the University of Pittsburgh Cancer Institute at Hillman Cancer Center, believes there might well be something behind those anecdotes involving skin cancers. (He had not read about the bladder cancer study, so he declined to comment on that.)

Although he is world renowned for his research to develop a vaccine against melanoma, his belief is based in part on what he has learned about dogs' amazing olfactory skills while watching his wife breed and compete German shepherds in the sport called Schutzhund.

The sport is a kind of triathlon for dogs, and one part of it requires that a dog do ground scenting, or track a trail laid over concrete, grass or even dirt. Sometimes the trails have been laid 24 hours earlier and in gale force wind.

The Kirkwoods also have dogs working avalanche rescue in Alaska, which requires air scenting.

How do dogs detect skin cancer? Kirkwood said the most plausible explanation is that up to a quarter of melanomas may have a break in the skin with traces of bleeding. "That is something all dogs smell. It's part of their carnivore background.''

But there could be a more complex explanation, he said, stemming from the molecular markers of certain cancers. Those markers, he said, "may be recognized by the immune system as what we call antigens, or substances that can be used in vaccine.

"In the most hopeful aspect of dog sniffing, it might well be that they have such high acuity of smell that they can smell things like the immune system can sense antigens," he said. "Their sense of olfaction may be in a sense akin to the immunological ability to recognize different things on the basis of molecular constituents."

The British study concluded that "tumor-related volatile compounds" released in urine give off an odor distinct from those associated with secondary effects of the tumor, including bleeding.

"We were very careful, in fact, to exclude the possibility that the dogs were simply keying in to the smell of blood, or of any other of the smells associated with inflammation, infection or tissue death," Willis said. "This was achieved during the training process by gradually introducing control urines which contained these smells, and then teaching the dog to ignore them.''

Marvit-McGlothlin, meanwhile, is enjoying her new son, John Wesley McGlothlin III, who was born on Oct. 6.

She returns to the skin doctor for a checkup in December, and if that checkup is good, she'll begin checkups on a yearly basis.