Everyone knows that dogs have great noses. We've put them to work detecting explosives, drugs, and missing people. Next assignment: sniffing out cancer.
Tessy, a yellow Labrador retriever, was destined to be a guide dog—she was born at the Guide Dogs for the Blind in San Rafael, California, after all. But when an infection left her blind in one eye, Tessy had to leave the family business. Thankfully, she still had the asset dogs are famous for—her nose. And with it, she's found a second career: sniffing out ovarian cancer in women.

The first medical journal to report on a dog behaving differently around an owner before the owner received a cancer diagnosis was The Lancet, which in 1989 described a woman whose border collie–Doberman mix wouldn't stop sniffing her mole. Because of the animal's persistence, she went to see a doctor, who identified the mole as a malignant melanoma. (The possibility isn't as crazy as it sounds: Scientists have long known that tumors release tiny amounts of chemicals different than those of healthy tissue.) In the early 2000s, British researchers set out to test dogs' sniffers. Using a method some police use to train bomb-detecting canines, they taught six dogs to identify the smell of bladder cancer in samples of patients' urine. The dogs' success rate wasn't stellar—41 percent—but it was enough to support additional research.

Within the past decade, researchers at Pine Street Foundation, a nonprofit cancer education and research group in San Anselmo, California, have taught dogs to identify the smell of breast and lung cancer on patients' breath. Their hope was that the biomarkers for cancer would be easier for the dogs to smell in the breath than in urine. The dogs were trained on breath samples that came from cancer patients; the sniffers earned a treat when they sat in front of the positive sample. "We think dogs are like people and perform best when they get positive feedback," says Michael McColloch, PhD, director of research at the Pine Street Foundation. The results of the study, published in 2006 in Integrative Cancer Therapies, were remarkable: The dogs achieved a success rate of 88 to 99 percent.

When you consider how sensitive dogs' noses are, the results aren't surprising—the average canine can detect scents 10,000 to 100,000 times better than the average human. They can pick up the smells at about one part per trillion, the equivalent of, say, being able to sniff out a single drop of chlorine in an Olympic-size swimming pool.

The next step is training a new set of dogs—Tessy included—to detect ovarian cancer, an often elusive disease that when found early has much higher survival rates. So far, the Pine Street Foundation dogs have done 25,000 scent trials for ovarian cancer. The researchers are collaborating with scientists at the University of Maine, who are trying to mimic the dogs' cancer-sniffing abilities with laboratory machines.

Nicholas Broffman, executive director of the Pine Street Foundation, foresees a time when women going in for annual physicals will give a Breathalyzer-like sample as routinely as they get their blood pressure taken or have a Pap smear. Whether the test tube that holds their breath samples will be sent away to a conventional lab or one that looks more like a dog run remains to be seen.

For now, the Pine Street canines work four hours a day, one day a week. "It's a mix of serious work, playtime, and hanging out with people," says McColloch. "These are all the things that get dog endorphins going."

And Tessy's schedule is much lighter than it would have been had she followed her original career path, says her owner, Paolo Pompanin, a master instructor at Guide Dogs for the Blind. It leaves her plenty of time for her other love—charging through powder on ski trips. "She jumps and jumps and jumps and jumps. She lets go completely."

Meet the most trustworthy dogs

From the June 2009 issue of O, The Oprah Magazine.



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