Which is better at detecting cancer, a laboratory or a Labrador retriever?
Consider the talents of Tsunami, a dog with attentive eyes and an enthusiastic tail wag for her trainer friends. University of Pennsylvania researchers say she is more than 90 percent successful in identifying the scent of ovarian cancer in tissue samples, opening a new window on a disease with no effective test for early detection that kills 14,000 Americans a year. When found early, there's a five-year survival rate of over 90 percent.
With 220 million olfactory cells in a canine nose, compared with 50 million for humans, dogs have long helped in search-and-rescue missions. Now, a growing body of evidence supports the possible use of canines by clinicians. The largest study ever done on cancer-sniffing dogs found they can detect prostate cancer by smelling urine samples with 98 percent accuracy. At least one application is in the works seeking U.S. approval of a kit using breath samples to find breast cancer.
"Our study demonstrates the use of dogs might represent in the future a real clinical opportunity if used together with common diagnostic tools," said Gian Luigi Taverna, the author of the prostate cancer research reported at the American Urological Association in Boston.
While smaller studies have long shown dogs can sniff out a range of illnesses, the question of whether they can be used on a large-scale basis has drawn skepticism. Questions remain on whether one type of dog is better than another, how to systemize their use and the financial viability of any such system. As a result, most current research is looking at how to copy the canine ability to smell disease either with a machine or a chemical test.
"Our standardized method is reproducible, low cost and noninvasive for the patients and for the dogs," said Taverna, the head of urology pathology at Istituto Clinico Humanitas in Rozzano, Italy, in an e-mail.
Taverna tested the ability of two professionally trained explosive detection dogs, Zoe and Liu, in 677 cases to assess their accuracy, according to his paper. The next step, according to Taverna, will be to extend the research into prostate cancer subgroups and to other urological malignancies. The results may one day be used to help develop an electronic nose that follows nature's lead in how a canine nose works, he said.
When dogs sniff for cancer, they are detecting the chemicals emitted by a tumor. These chemicals are referred to as volatile organic compounds, or VOCs. VOCs have been found in the breath of lung cancer patients and colon cancer patients, as well as in the urine of prostate cancer patients. The most recent findings have spurred increased interest in dog cancer — detection research, including efforts to develop devices that can mimic the animal's exquisite olfactory system.
Dina Zaphiris, a nationally recognized dog trainer, is leading the charge for Food and Drug Administration clearance of a system that would use the olfactory talents of dogs in medical care. In 2009, Zaphiris founded the In Situ Foundation, a nonprofit organization that trains cancer-sniffing dogs and conducts research in the field.
Her organization is submitting an FDA application for approval of a canine medical scent detection kit. In her system, patients exhale through a tube on to a cloth, which captures molecules, or VOCs, of a malignancy. Trained dogs would then sniff the cloths for their presence. The dog screening would be an "early warning test," she said.
Zaphiris isn't alone in her quest. At the University of Pennsylvania School of Veterinary Medicine, researchers are studying whether dogs can find ovarian cancer in tissue and blood samples. If so, it would be a breakthrough for a difficult disease.
"We're trying a multiprong approach," including the dogs and laboratory efforts, "to determine if there's some signature in blood in women with ovarian cancer so we can develop a detection system," said Cindy Otto, director of the university's Penn Vet Working Dog Center in Philadelphia. "We're using the dogs because we know the dogs are much more sensitive than any of our chemical techniques."
The goal is to one day produce a new screening system or sensor to detect ovarian cancer's odor signature, Otto said.
Tsunami, the German shepherd named for her tendency to come at you when you least expect it, has been particularly successful, Otto said. When she's working, she becomes a quiet, pensive animal. She works very slowly, circling a wheel containing blocks of samples. She sniffs, she stops, she thinks, Otto said.
When she identifies cancer, she sits; that's the sign.
"She's very serious about it all," Otto said.