Dogs Can Detect Breast Cancer, But Don’t Expect Dr. Dog Anytime Soon


Most of us have heard about the amazing talents of our canine friends. They can sniff out bombs, help those with special needs, protect police officers, and even detect cancer. But when an entire country gets together to recognize a special dog hero, we know it’s time to pay extra attention.

On December 7, 2017, Nykios, the 3-year-old Malinois Shepherd, was given a special honor in Paris, France. Nykios was recognized at the Trophée des chiens héros (Trophy for Heroic Dogs) ceremony, France’s first awards ceremony for heroic dogs.

Nykios’s claim to fame? He can detect breast cancer. This smart pup was trained for just 6 months before beginning his prestigious career at the Curie Institute in Paris. Nykios was trained to detect breast cancer by sniffing cloths that had either come into contact with a healthy breast or a cancerous one. Nykios can pick out the cloths that came into contact with breast cancer from the ones that didn’t with 90%-100% accuracy.

Kdog, the group that trained Nykios, hopes that someday cancer-sniffing dogs will be available to those who live in countries with less access to cancer-screening equipment.

Drawbacks of Cancer-Sniffing Canines

A dog’s nose is no joke. Dogs can detect smell in parts per trillion. Think of it like this—if there were one cc of blood in a swimming pool the size of 20 Olympic-sized pools, a dog would be able to smell it.

Cancer has a smell that can sometimes be detected by humans in its later stages, but dogs can detect cancer in earlier stages, sometimes even before traditional screenings are able to. But they’re not perfect.

Photo: AdobeStock/chalabala

Photo: AdobeStock/chalabala

One of the challenges is communicating with the dog. When a dog is trained to identify a scent like marijuana, they are looking for a specific, mostly isolated scent. But the smell of cancer in a person’s breath or fluids is mixed with a person’s other organic smells, and it’s difficult to train the dog to understand that they are looking for the cancer scent, not the unique scent of a specific person.

And dogs, like people, have bad days, but it may be harder to recognize a bad day in a dog. Dogs don’t seem to work as well after lunch, and they can be affected by stress. That’s understandable, but a cancer screening has to be consistently accurate.

In real world scenarios, if a dog were to incorrectly identify cancer and then receive a reward from a handler who didn’t know better, the handler would be reinforcing an incorrect behavior. And while trained cancer-sniffing dogs are excellent at choosing one diseased sample from a set, studies have shown that testing dogs with varying numbers of diseased samples in the set decreases their accuracy. The added variable (the unknown number of diseased samples) makes the dogs less reliable, and if dogs were used in an actual screening, doctors and handlers wouldn’t know if a patient’s sample was positive or negative. A screening has to be accurate in order to be useful.

Another drawback is that dogs are essentially playing a game when they’re sniffing samples. Not finding a positive sample, and therefore not being rewarded, may cause stress and reduce accuracy. For example, during 9/11 recovery efforts, search and rescue dogs were occasionally allowed to find staged fake bodies so that they could be rewarded and avoid becoming stressed.

Still, dogs may have an important role to play in early detection. Even untrained dogs sometimes alert their owners to cancer or other dangers (like Max, for example), and dogs have helped scientists understand that cancer does have a specific smell. If a machine could be designed to identify cancer from the unique chemical signature of its smell, it could help doctors detect cancer earlier and more accurately.

So don’t be surprised if someday your cancer screening involves a machine called the Fido 9000. Our furry cancer-sniffing friends may teach us what to look for so that we can create a screening that is 100% reliable, and then the canine crew can retire to tail-chasing and playing with squeaky toys. They will have earned it!

Next: Maureen thought her dog Max was sick, but he was trying to tell her that she had breast cancer.


Katie Taylor started writing in 5th grade and hasn't stopped since. Her favorite place to pen a phrase is in front of her fireplace with a cup of tea, but she's been known to write in parking lots on the backs of old receipts if necessary. She and her husband live cozily in the Pacific Northwest enjoying rainy days and Netflix.
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