Published February 01, 2011
Retrieving a slobber-covered tennis ball, bringing in the morning newspaper ... saving lives by sniffing out cancer?
Japanese research has added to mounting evidence that dogs can be trained to use their powerful sense of smell to detect cancer.
It focused on a labrador which, the study showed, could accurately detect colorectal cancer by sniffing samples of a person's breath or their feces.
The research, published online by the British Medical Journal, follows earlier studies into dogs which could detect melanoma as well as bladder, lung, breast and ovarian cancers.
Dr. Hideto Sonoda said the latest research confirmed a "specific cancer scent does indeed exist and that cancer-specific chemical compounds may be circulating throughout the body".
"We used the excellent ability of dogs to distinguish between different scents to examine whether odor material can be used in the diagnosis of colorectal cancer," said Sonoda, from the Fukuoka Dental College Hospital.
"This study represents the first step towards the development of an early detection system using odor materials from patients with colorectal cancer."
The labrador, trained by sniffing breath samples from people with the cancer, was put through an array of blinded smell tests over several months to avoid fatigue.
The dog was presented with breath and stool samples from more than 300 volunteers, 48 of whom had confirmed bowel cancer while others had recovered from the disease or they had benign polyps.
The dog's handler, and the lab assistants, did not know which of the samples were from people with active colorectal cancer.
The volunteers also included smokers and those with gut problems, such as ulcers, but this did not pose a problem for the dog.
It identified the samples from people with active cancers with 95 percent accuracy for the breath test, and 98 percent accuracy for the stool test, compared to what a doctor could see with a colonoscopy.
The dog was "rewarded with a tennis ball" during the sniff tests, though Sonoda warned this non-invasive approach to colorectal cancer testing was unlikely to appear in a doctor's clinic anytime soon.
"It may be difficult to introduce canine scent judgment into clinical practice owing to the expense and time required for the dog trainer and for dog education," Sonoda said.
"It is, therefore, necessary to identify the cancer-specific volatile organic compounds detected by dogs and to develop an early cancer detection sensor that can be substituted for canine scent judgment."
Professor Ian Olver, from Cancer Council Australia, said a "mechanical equivalent" of the dog's cancer-attuned nose would represent a significant breakthrough.
"If you're going to apply this to a population you need to have something a little less high-maintenance (than a dog)," he said.
"But this does show us how clever animals can be and how they can give us the lead to do other things."