In August 2009, Dr. Claire Guest’s labrador began behaving peculiarly. Usually a gentle dog, Daisy -- who Guest had been training to detect diseases with her keen sense of smell -- refused to get into the car, and instead collided into Guest a few times before “prodding” her in the chest.
Daisy’s strange behavior prompted Guest to check the area where the dog had nudged her. Tests later revealed that she had early-stage breast cancer. Her doctor told her she was “incredibly lucky” to have found it so early.
“All I could think was, what a difference Daisy has made,” Guest told The Telegraph in 2014. “I might have had to have aggressive chemotherapy. I might not have survived. That’s what made me decide: right, we’ve got to discover what’s going on.”
Six years on, a cancer-free Guest is one of the leaders in the field of disease-detecting canines. Her organization, Medical Detection Dogs, recently gained approval from Britain’s National Health Service to conduct a landmark clinical trial to test dogs’ ability to sniff out prostate cancer cells.
NBC News called the trial “groundbreaking.”
Earlier studies have suggested that dogs’ incredible sense of smell can detect subtle odors known to be associated with many cancers, such as melanoma and cancers of the breast, bladder and lung. In the case of prostate cancer, Guest says initial tests have shown trained dogs to have a detection accuracy rate of more than 93 percent.
“Our dogs have higher rates of reliability than most of the existing tests. We know their sense of smell is extraordinary. They can detect parts per trillion -- that’s the equivalent of one drop of blood in two Olympic-sized swimming pools,” she told The Guardian. “We should not be turning our backs on these highly sensitive bio-detectors just because they have furry coats.”
Medical Detection Dogs says it typically trains its canines for about six months before the animals are able to reliably sniff out trace amounts of cancer cells in urine samples. Once trained, the dogs will either stop and sit down by the sample, lick the bottle, or bark to indicate they’ve detected the scent of cancer cells.
According to Guest, trained dogs are able to detect this scent almost instantly.
“These dogs have the ability to screen hundreds of samples in a day; it's something they find very easy, they enjoy their work. To them it's a hunt game -- they find the cancer,” she told Reuters.
Prostate cancer is the most common cancer in men in the U.K., and one of the most common causes of cancer death. The Prostate-Specific Antigen test, or PSA, is currently used to detect the disease; however, the procedure is known to have a high false positive rate, which means many men end up undergoing the invasive test unnecessarily.
Scientists say cancer-sniffing dogs may be able to help reveal inaccuracies in the PSA test, and eventually help in the development of much better cancer screening services, such as an “electronic nose” that could help sniff out cancer cells the way dogs’ noses do.
Researchers also hope that dogs’ acute sense of smell could be used in the detection of many other diseases.
“This is opening a new way of diagnosing diseases and conditions in the future,” Guest told Reuters.
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