The capacity of dogs to be man's best friend seems to know no bounds.
A new study finds that dogs can detect lung and breast cancer in breath samples by picking up on chemical differences that linger in the breath of a person with cancer.
"When we heard anecdotally that there was a device out there that might be able to detect cancer at its earliest stages, before it even shows up on an MRI [magnetic resonance imaging], it was something we wanted to pursue," said Nicholas Broffman, executive director of the Pine Street Foundation, a nonprofit group in California that conducted the study. The group helps cancer patients who are facing tough treatment decisions.
In Broffman's study, three Labrador retrievers and two Portuguese water dogs were trained to either sit or lay down in front of breath samples from lung and breast cancer patients, while ignoring those of healthy individuals.
"These were not super dogs," said Broffman. "They were just ordinary household pets."
The trial comprised of breath samples from 55 patients with lung cancer, 31 with breast cancer, and 83 healthy people. The samples were captured in special tubes.
All cancer patients had recently been diagnosed through conventional methods, such as mammograms or CT scans, but had not yet begun chemotherapy. And the trial samples were different from the ones used to train the dogs.
The results show the dogs were 88 percent to 97 percent accurate in identifying both early- and late-stage breast and lung cancers.
Catching cancer early increases survival rates and allows for treatment with lower toxicity, experts say.
The ability of dogs to detect cancer was first discovered in 1989, and reported in the medical journal The Lancet. A woman's pet had alerted her to the presence of melanoma by constantly sniffing the skin lesion on her leg. Subsequent studies have shown dogs can smell melanoma and bladder cancer.
"I think all of these [studies and observations] are saying this ought to be looked at more carefully and ought to be taken seriously," said James Walker, director of Florida State University's Sensory Research Institute in Tallahassee.
He says a dog's nose is so powerful it can detect odors 10,000 to 100,000 times better than a human nose can.
Later this year, he plans to launch a study on canine detection of bladder cancer.
Veterinarian Larry Myers, from Auburn University in Alabama, is currently working on four canine-cancer detection projects, and thinks that dog eventually could be used to screen for cancer at local health fairs or in Third World countries.
"Everybody needs to be careful and not overstate how wonderful these [studies] are," said Myers. "We need to approach [this type of research] slowly, cautiously and scientifically."