Can Dogs Detect Cancer?

Before my diagnosis and in the weeks after, my dog – an eight-year-old pug named Tang Tang – stuck pretty closely to my side. I didn't think anything of it at the time – in the first place, because I'm his owner, but also because I'm typically an anxious mess, and Tang, a former therapy dog, was like a divining rod for finding anxious people.

Another reason he was trying to squeeze onto my lap?

But looking back, having learned a great deal about different kinds of cancers, I wonder if there wasn't another reason he was constantly trying to squeeze himself onto my lap.

According to a recent study published in the journal Experimental Biology, dogs in a clinical setting were able to detect the incidence of blood cancer in a human patient with a 97 percent rate of accuracy.¹ Other studies have shown that dogs are able to detect melanoma, lung, and breast cancers, even in their earliest stages.^2,3

How could dogs detect cancer?

But how does this happen? Scientists say that all cells release something called a volatile organic compound, or VOC.⁴ Cancer cells give off a different level of VOCs, something that canines, with their vastly superior sense of smell, are able to detect. At some stages of the disease, VOCs can be detected in patients' breath or urine. Dogs who detect high or changing levels of VOCs can attempt to alert their owner, sometimes by gnawing on a cancerous mole or licking a part of the body.^2,5

Challenges with research around dogs and cancer

Literature has shown numerous times that dogs have the ability to detect cancer – but proving it in the confines of a laboratory study can be challenging. In one double-blind study, when dogs were asked to alert to the smell of cancer on someone's breath, neither the researcher nor the trainer knew whether the specimen the dog was sniffing, in fact, had cancer. As a result, no one was able to provide positive reinforcement to the dogs, which confused them and stressed their trainers (understandably). Still, research around dogs and cancer continues to develop.

A story that convinced me

Looking back, I can't pinpoint a time where I thought Tang was alerting me to something happening in my bladder or elsewhere in my body. However, about a year after my TURBT, I heard a story that further convinced me of dogs' extraordinary ability to detect cancer: A friend of the family, Jim, had discovered a tennis-ball-sized tumor in his lung during a CAT scan for an unrelated ailment. Throughout chemotherapy, his dog had taken to perching on his lap with his paws on Jim's chest, as though he was alerting people to an undetected problem. He did this for weeks, without fail, until one day he stopped. At the next oncologist appointment, doctors found that Jim's tumor had almost completely vanished.

Man's best friend, indeed.