Dogs may be able to sniff out the presence of cancerous cells through a human’s breath. Not only does their sense of smell make cancer detection possible, but research suggests that dogs can be trained actively to sniff out the cancer.
It might come as a surprise that a dog’s olfactory abilities are so great that he can potentially sniff out cancer in humans. This double smelling system allows trained dogs to detect cancer’s unique odors, called volatile organic compounds.
Dogs’ powerful noses have 300 million sensors, compared with a human’s measly 5 million. In addition, dogs have a second smelling device in the backs of their noses that we don’t have, called, ‘Jacobson’s organ.’
Studies of dogs and cancer detection are based on the fact that cancerous cells release different metabolic waste products than healthy cells in the human body. The difference of smell is so significant that the dogs are able to detect it even in the early stages of cancer. Dogs are able to identify the chemical traces in the range of parts per trillion.
Some studies have confirmed the ability of trained dogs to detect the skin cancer melanoma by just sniffing the skin lesions. Some researchers have also proven that dogs can detect prostate cancer by simply smelling patients’ urine.
A study presented at the annual meeting of the American Urological Association in Orlando showed that dogs can almost unerringly detect prostate cancer in urine samples, also in Berlin, a group of researchers trained some dogs to detect the presence of various types of cancer, including ovarian cancer, bowel cancer (which apparently smells different from both endometrial cancer and cervical cancer), as well as bladder cancer, skin cancer, lung cancer and prostate cancer.
In the UK, Lucy, a cross bred dog between a Labrador retriever and an Irish water spaniel, learned to sniff out bladder, kidney and prostate cancer, and was even used in a study. Over the years, she has been able to detect cancer correctly more than 95% of the time which is more effective than some lab tests used to diagnose cancer.
Now, Lucy is part of one of the largest clinical trials of canine cancer detection. A British organization, Medical Detection Dogs, has eight dogs sniff out 3,000 urine samples from National Health Service patients to see whether they can discern who has cancer and who doesn’t, CNN reports.
Dogs have 25 times more smell receptors than humans, boosting their smelling ability by 100,000 times. The brain of a human is dominated by the visual cortex, but the brain of a dog is controlled by the smell or olfactory cortex, which is approximately 40 times larger than that of a human.
Furthermore, the olfactory bulb in a dog has a large number of smell-sensitive receptors, which range between 125 to 220 million, and it is a hundred thousand to a million times more reactive than that of humans.
It took humans thousands of years to figure this out. In 1989, doctors at King’s College Hospital in London wrote in The Lancet about a woman whose dog persisted in smelling a particular mole on her leg. That mole turned out to be early-stage malignant melanoma.
Over the next 26 years, studies from France to California to Italy have concluded that dogs really can detect the smell of cancer.