It’s important to recognize that science has not shown in any definitive capacity that dogs or other pets can smell or positively indicate cancer.
However, there are many people who swear that their canine companions pawed, jumped or barked at them repeatedly in a noticeably out-of-the-ordinary way, so much so that they got checked out—and lo and behold, they were diagnosed with cancer.
For example, in early 2014, BBC reported on the story of a 9-year-old mutt who alerted her owner to a lump in her breast that was previously undetected by mammogram; that same year, a dog who competed in the Westminster Dog Show was credited in the news with saving his owner’s life when he was just a puppy.
In 2009, a psychologist and dog trainer who believed in the power of pets’ noses before it affected her directly had a similar encounter. As Dr. Claire Guest told the New Republic, her dog Daisy began behaving strangely while she was, coincidentally, working on a study to investigate whether or not domesticated dogs could smell breast cancer. A few doctors appointments later, Dr. Guest was diagnosed with cancer in her breast that was, she says, unlikely to have been found by human devices since the tumor was so deep into the breast.
Even earlier, the “Lancet letters,” as they are known, document two cases in 1989 and 2001, respectively, within the journal The Lancet where dogs alerted their owners to skin cancers of which they were otherwise unaware. (Dr. John Church, who co-authored the latter went on to endorse a charitable organization founded by Dr. Guest called the Medical Detection Dogs which aims to train dogs to detect medical issues like low blood sugar as well as learn more about the potentials of cancer-sniffing pups.)
How is this possible? While it hasn’t been proven yet, dogs’ powerful capability to smell, combined with the distinctive smell of the volatile organic compounds within cancer and cancerous tumors, may allow dogs to be trained to help identify such diseases before they are evident to people. We don’t know what potential this has, but harnessing the smell of disease is an exciting medical arena.
In the meantime, pets have another useful purpose when it comes to working with people with cancer—acting as emotional support and therapy animals to calm nerves and lift spirits. Organizations like the Good Dog Foundation allow for patients undergoing treatments like chemotherapy to be distracted and comforted by well-trained and certified pups, bringing a little joy when it’s needed most.