SAN ANSELMO, Calif. -- Researchers in California have trained dogs to detect lung and breast cancer in breath samples from people with 88 to 99 percent accuracy, according to a new study.
The studies show that cancer cells emit chemicals or molecules that are different from those in normal cells, and more research is needed to determine just what those chemicals are -- and whether they could help doctors find cancers earlier.
''The challenge now is if technology can jump over the bar the dogs have set," said Michael McCulloch, research director for the private, nonprofit Pine Street Foundation in San Anselmo, Calif., which conducted the research.
For now, very little is known about the chemicals dogs apparently are detecting in diseased cells or how the dog's olfactory system is able to pick up on them. Previous studies had shown that dogs can detect skin and bladder cancer.
Ultimately, the Pine Street Foundation study ''means there's something we can now key into that might allow for early detection of cancer," said Thomas Schoenfeld, research associate professor of physiology at the University of Massachusetts Medical School, who has studied the olfactory systems of rodents.
''Dogs have opened the door," he said.
The study, which will be published in the March issue of the medical journal Integrative Cancer Therapies and is available at www.pinestreetfoundation.org., is the first to test whether dogs can detect cancer by sniffing samples of exhaled breath collected in tubes.
The canine ''diagnostic tools" -- two Portuguese water dogs and three Labrador retrievers -- were borrowed from their local owners and Guide Dogs for the Blind. The dogs were trained for roughly three weeks using the ''click and reward" method.
When the dogs successfully detected which tubes held breath samples from cancer patients they heard a click and received a food reward. The dogs were trained to sit or lie down when they detected a diseased sample.
After conducting more than 12,200 separate ''dog/breath sample interactions," researchers reported the dogs had an 88 percent accuracy rate in detecting breast cancer and a 99 percent accuracy rate in detecting lung cancer.
There were a few surprises after the study was completed.
Two of the dogs that had been trained for the study spontaneously reacted to people on the street, and one of them may have saved the life of a dog trainer at a dog show.
''Our dog sat down at a dog show at a time when the dog was supposed to stand up," said McCulloch. ''That person went to her doctor and learned she had a melanoma."