Dogs' Noses Know More Than Doctors About Cancer Detection

Dogs are highly accurate sniffing out various diseases and outperform humans

Posted Jul 11, 2015

A recent essay in New Scientist by Liz Bestic called "The cancer sniffers: Dogs could be the best tool for diagnosis" is a very good summary about what we know about the ability of dogs to sniff out cancer (the title in the print edition is "The nose knows"). Because Ms. Bestic's article currently is only available to subscribers, here's a brief summary and some snippets. I was really impressed to learn that the latest research truly shows just how good dogs are in whiffing trouble. In a previous essay I wrote called "Butts and Noses: Secrets and Lessons from Dog Parks," you can learn more about what we know and don't know about the incredible dog schnoz that winds up sniffing and snorting in many different places, some that make humans cringe in disgust or embarrassment

Meet Ollie the Labrador researcher

Ms. Bestic begins, "Anecdotes of dogs that can sniff out cancer have been doing the rounds for years, and now the urban legend is being subjected to scientific scrutiny - AT 8 o'clock every morning, Ollie leaves his house and sets off on the short drive to work at the local laboratory. Eager to get to going on his latest project, he greets his colleagues enthusiastically before donning his regulation lab coat and heading for the testing room. Here, Ollie begins his tour of a carousel which has small phials of urine attached to each arm. His job is simple – to take a gentle sniff of each one and let his boss know which of the samples contains a particular type of cancer. It is precise work, but Ollie gets it right over 90 per cent of the time. Not bad for a Labrador."

Ollie is one of many dogs who are being used to diagnose cancer by sniffing volatile organic compounds (VOCs) that indicate various diseases. Hundreds of VOCs "are excreted by the body in sweat, urine, breath and other body fluids. The VOCs we excrete are a reflection of the metabolic processes going on in our cells, and combine to give us an individual 'odour fingerprint' that differs with age, diet and gender. It also changes with health, because diseased cells metabolise differently to healthy ones."

It's been suggested that dogs seem anxious when sniffing VOCs associated with cancer. To test whether dogs are really good and reliable diagnosticians, a team of researchers from the UK's High Wycombe Hospital conducted a systematic study, the results of which were published in an essay called "Olfactory detection of human bladder cancer by dogs: proof of principle study." Their conclusions read as follows: "Dogs can be trained to distinguish patients with bladder cancer on the basis of urine odour more successfully than would be expected by chance alone. This suggests that tumour related volatile compounds are present in urine, imparting a characteristic odour signature distinct from those associated with secondary effects of the tumour, such as bleeding, inflammation, and infection." Better methods of training dogs used in more recent studies have produced more accurate results. 

Because VOCs appear in the body early in very early stages of cancer, it was thought that dogs could be used to make early diagnoses. While some cancers such as cervical cancer can be diagnosed early through screening, others, such as prostate cancer, are more difficult to spot. A study using two dogs conducted by Gian Luigi Taverna at the Humanitas Clinical and Research Centre in Milan, Italy, showed that "When asked to analyse 900 urine samples, both dogs managed to accurately identify those that came from men with prostate cancer at various stages around 98 per cent of the time. Overall the dogs had 16 false positives and four false negatives – a much better strike rate than PSA tests. With this level of accuracy, it should be possible to use dogs to reduce the number of biopsies and identify people at risk, says Taverna." The complete results of this study can be seen in an essay called "Olfactory System of Highly Trained Dogs Detects Prostate Cancer in Urine Samples" published in The Journal of Urology

It's heartening to learn that research is being conducted to learn if dogs can reliably sniff out ovarian cancer that shows very few symptoms, colon cancer, lung cancer, and breast cancer. Researchers note, "The final hurdle will be to apply the dogs' sensitive snouts to real life screening and diagnosis. There are lots of logistical reasons why the role of dogs will always remain behind the scenes, rather than in the doctor's office, but nonetheless they are about to start work in screening and testing samples from real patients. 'We believe we can apply the dog's superior olfactory system to screening protocols and introduce this tool into clinical practice,' says Fabio Grizzi, one of the co-authors of the Italian prostate cancer study."

"If the dogs can't find VOCs in the sample, nobody can"

Highly regarded researchers are extremely keen on using dogs' noses to diagnose cancer. George Preti, who works at Pennsylvania State University's Monell Chemical Senses Center, claims, concerning lung cancer detection, "Dogs are far more sensitive than any technique I know of ... They can demonstrate that an odour signature is present, even though we may not smell it or see it with our instruments." Claire Guest, CEO and director of operations at Medical Detection Dogs, "is convinced that the dogs remain the best bet for picking up a whiff of disease where other tests fail. 'We are not talking about a couple of volatile markers that constantly appear at the same level. We're looking at complex pattern recognition' she says. 'If the dogs can't find VOCs in the sample, nobody can.'"

Disease detection by dogs' noses is an incredibly exciting and important area of study, and I look forward to learning more about what dogs' noses really know.

Marc Bekoff's latest books are Jasper's story: Saving moon bears (with Jill Robinson), Ignoring nature no more: The case for compassionate conservationWhy dogs hump and bees get depressed, and Rewilding our hearts: Building pathways of compassion and coexistenceThe Jane effect: Celebrating Jane Goodall (edited with Dale Peterson) has recently been published. (marcbekoff.com; @MarcBekoff)