London - Dr Claire Guest was preoccupied with thoughts about work as she took her dogs for a walk one grey February evening in 2009.
A long-term dream to use sniffer dogs to detect early signs of cancer had hit an impasse.
Claire, a British animal behavioural psychologist, was convinced the animals could sense abnormal cancer cells through smells emitted by the skin, urine or even in the breath.
Her first clinical research, published five years earlier, had shown it was possible to train dogs to detect cancer in samples supplied by patients.
Since then, the accuracy of the dogs’ detection had risen to 73 percent. But Guest’s findings were being dismissed by some in the medical establishment – and her plan for a team of dogs to become a “second line” detecting unit, specialising in hard-to-spot cancers such as pancreatic and prostate, was dismissed as hokum. As Claire recalls: “One leading cancer specialist said publicly: ‘You can’t possibly have a dog in every doctor’s surgery, so I can’t see the relevance’.
“But what I envisaged were dogs in satellite units, across the country. They don’t need direct contact with individuals, because samples of breath and urine can be brought to the dogs to record their reaction.”
That February evening, Claire opened the boot of her car to allow her dogs out. While Tangle, a cocker spaniel, and a friend’s Yorkshire terrier jumped out of the car and ran into the park, their tails wagging, Daisy, a labrador, refused to follow.
As Guest, now 50, recalls: “Daisy seemed to be pawing at my chest. She bumped against my body repeatedly – I pushed her away, but she nuzzled against me again, clearly upset.
“She pushed me so hard that it bruised me. Her behaviour was totally out of character – she was normally such a happy dog, who would never hesitate to race after the other dogs.”
“I felt the tender area where she’d pushed me, and over the next few days I detected the tiniest lump.”
A few days later she went to her GP, who referred her to a consultant. He thought it was a cyst, but said he would do a mammogram to be sure.
“He was correct – the bump was a perfectly harmless cyst,” says Claire. “But further in the breast tissue was a deep-seated cancer.”
It was caught very early and she had a lumpectomy and some lymph nodes removed, as well as receiving six months of radiotherapy.
“I was 46 and the specialist told me that by the time a lump had become noticeable, this cancer would already have spread and my prognosis could have been very different.
“Just as I was doubting the future of dogs being used to detect cancer, my own pet labrador saved my life.”
Now, five years and several trials later, Daisy has sniffed 6 000 samples of urine and detected more than 551 cases of cancer with a diagnostic accuracy of 93 percent.
Claire’s charity, Medical Detection Dogs, now has 12 dogs who live with host families and come to work from Monday to Friday at the charity’s headquarters near Milton Keynes, detecting traces of cancer from urine and breath samples. They are trained by sniffing urine samples of people with cancer and rewarded when they single out these samples from other urine from non-cancer sufferers.
Claire says: “We published the first report into dogs detecting cancer in 2004 in the British Medical Journal, showing that our dogs correctly identified bladder cancer in 22 out of 54 cases – our success rates are now 93 percent.”
Using dogs to diagnose a disease with such potentially serious consequences as cancer may sound bizarre, but the concept is seriously being considered by scientists.
In 2010, for example, Japanese researchers showed that dogs can detect colorectal cancer from a breath sample, while in 2012 the European Respiratory Journal published research that found dogs could identify lung cancer in breath samples.
“A lot of cancers are difficult to detect in early stages,” says Claire. But malignant cells produce changes in volatile organic compounds, and it’s these compounds which dogs are believed to detect in urine samples.
“Dogs can detect odours at concentrations as low as one part per trillion, identifying scents which the human nose could never detect,” says Claire. “We have 5 million sensor receptors dedicated to smell – dogs have 300 million.”
Scientists are now developing electronic systems (e-noses) that mimic the way dogs detect the smell of cancer.
Medical Detection Dogs is helping in this work by supplying statistics on reliability of dogs and their findings on how long the volatile compounds survive once exposed to air, for instance. – Daily Mail
For more info, visit www. medicaldetectiondogs.org.uk