Researchers at the University of Pennsylvania in the US say a labrador dog is more than 90 per cent successful in identifying the scent of ovarian cancer in tissue samples.
This opens a new window on a disease with no effective test for early detection and that kills tens of thousands of women a year around the world. When found early, there is a five-year survival rate of more than 90 per cent.
With 220 million scent cells in a canine snout, compared with 50 million for humans, dogs have long helped on search-and-rescue missions. Now, evidence is growing to support the possible use of canines by clinicians. The largest study done on cancer-sniffing dogs found they could detect prostate cancer by smelling urine samples with 98 per cent accuracy.
At least one application has been lodged seeking United States 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," Gian Luigi Taverna, the author of the prostate cancer research was reported yesterday as telling the American Urological Association in Boston.
While smaller studies have shown dogs could detect a range of illnesses, the question of whether they could be used on a large-scale basis to find disease has been received with scepticism.
Questions remain on whether one type of dog is better than another, how to systemise their use and the financial viability of any such system. As a result, most research is looking at how to copy the canine ability to smell disease either with a machine or a chemical test.
"Our standardised method is reproducible, low-cost and noninvasive for the patients and for the dogs," said Taverna, the head of urology at Istituto Clinico Humanitas in Rozzano, Italy.
Taverna tested the ability of two explosive detection dogs in 677 cases to assess their accuracy, according to his paper.
He said the next step would be to extend the research into prostate cancer sub-groups and to other urological malignancies. The results may one day be used to help develop an electronic nose that followed how a canine snout works, he said.
When dogs sniff for cancer, they are detecting the chemicals emitted by a tumour, referred to as volatile organic compounds, or VOCs.
VOCs have been found in the breath of lung cancer and colon cancer patients, as well as in the urine of prostate cancer patients. The most recent findings have spurred increased interest in dog detection research, including efforts to develop devices that can mimic the animal nose.
Dina Zaphiris, a dog trainer who works with canines on federally funded studies in detecting early cancer in humans, is leading the push for official clearance of a system that would use the talents of dogs in medical care.
In 2009, Zaphiris founded the In Situ Foundation, a non-profit organisation that trains cancer-sniffing dogs and conducts research in the field.
Her organisation is submitting an application for approval of a canine medical scent detection kit. In her system, breast cancer 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, possibly used in connection with a mammogram for reviewing results before proceeding to a biopsy operation.
Zaphiris is not alone in her quest to get dogs involved in medical care. 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 multi-prong approach including the dogs and laboratory efforts, to determine if there is some signature in blood in women with ovarian cancer so we can develop a detection system," said Cindy Otto, director of the university's working dog centre in Philadelphia.
"We're using the dogs because we know the dogs are much more sensitive than any of our chemical techniques."