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Clever dogs sniff out bladder cancer
Dogs have been trained to detect bladder cancer by sniffing urine, using their acute sense of smell to identify a tiny but characteristic odour released by tumours, a study says.
The dogs were then put through their paces in a carefully-devised test. They had to detect a urine sample from a bladder-cancer patient among six "control" samples, nine times over. Taken as a group, the dogs correctly spotted the positive sample 22 times out of 54 -- a success rate of 41 percent. The performances ranged from one out of nine by a six-year-old male mongrel to five out of nine by two working-strain cocker spaniels, a male aged 18 months and a female aged two years. The team, who report their work in the British Medical Journal (BMJ), say the outcome is "proof of principle". It opens up intriguing paths into detecting early-stage cancer through smell, rather than through chemical tests, scans or invasive diagnostics as is the case today. The inspiration for the experiment dates 15 years, when a pair of British dermatologists wrote a letter to The Lancet in April 1989 to describe a bizarre case in which a worried dog saved her owner's life. The animal persistently sniffed, and eventually tried to bite, a lesion on the woman's leg. Thus prompted, she went to the doctor, who found that it was skin cancer in its earliest stages. She was successfully treated. Innovative technological work into cancer-sniffing has also been unfolding. University of Rome scientists last year tested a prototype "electronic nose" that proved to be 100-percent accurate in a breath test of 35 people with advanced lung cancer and 25 others who were healthy. The device works in the same way as hygiene "sniffers" that are used on the production line in hi-tech food factories to detect the chemical signature of rotting ingredients. These sensors comprise a quartz crystal coated with metal-containing dyes that bind to specific organic (i.e. carbon-based) chemicals. The binding very slightly changes the weight of the crystal, causing it to vibrate at a different frequency, thus triggering a signal. The theory behind cancer sniffing is that tumours release volatile organic compounds as they grow. Even though the amounts are only tiny, they have a specific signature that can be detected if the olfactory power is strong enough to sense and discriminate.
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