Now, mounting evidence suggests that dogs can also play a part, directly or indirectly, in detecting cancer in humans.
The Science Behind a Dog’s Sniffer
In her book
Nose of a Dog, research scientist Alexandra Horowitz notes that “most of what the dog sees and knows comes through his nose.” Depending on the breed, a dog’s nose has around 125 million to 300 million scent glands, while a human’s nose has around five million scent glands. That means that a dog’s sense of smell is around 1,000 to 100,000 times more sensitive than a human’s.
Research indicates that dogs are capable of detecting tiny traces of odors created by different diseases. How tiny? Around one part per trillion, or the equivalent of one teaspoon of sugar in two Olympic-sized swimming pools.
How Do Dogs Act When They Smell Cancer?
“The ability of dogs to detect
melanoma, a potentially fatal skin cancer, has been formally studied and confirmed,” says Ashley Stenzel, PhD, a Roswell Park postdoctoral fellow. Dr. Stenzel notes that in case studies, dogs persistently sniffed, licked and nipped at melanoma lesions on their owners’ skin, even through clothing, prompting the owners to identify the cancerous sites and seek care from clinicians. “Given that melanoma is a cancer presenting with lesions on the skin, it would be logical for dogs to be able to detect a lesion,” Dr. Stenzel says. “However, the use of canine olfactory detection has also been studied in other examples of cancer.”
Lauren credits her dog, Victoria, for calling attention to a bump on her nose, which turned out to be basal cell carcinoma.
In one widely noted anecdotal case, Lauren Gauthier, founder of Magic's Mission hound rescue organization, reported that Victoria, her adopted Treeing Walker Hound, “persistently sniffed and stared at what seemed like a pimple on my right nostril. It was so odd and she was so persistent that I finally decided to have it checked out.” The "bump" ended up being
basal cell carcinoma, a common type of skin cancer. “As soon as I had
Mohs surgery to remove the cancer, Victoria’s strange behavior stopped.”
Claire Guest, MSc, DHP, BCAh, CEO of Medical Detection Dogs, recalls that Daisy, her Fox Red Labrador, who is trained to sniff out cancer in the lab, kept staring and pawing at her chest. While trying to decipher Daisy’s behavior, Dr. Guest discovered a lump that turned out to be a malignant tumor deep in her breast.
In
Being a Dog, Horowitz describes a Dachshund puppy that repeatedly sniffed her owner’s armpit. Eventually the woman found a lump in her armpit, leading to a breast cancer diagnosis.
Can Dogs Be Trained to Detect Cancer?
Possibly. Some organizations researching this include the
University of Pennsylvania Veterinary School’s Working Dog Center and Medical Detection Dogs, in the United Kingdom. In various experiments, dogs have detected:
- Breast cancer and lung cancer, by sniffing the breath of patients. In these studies, it is thought that the dogs sensed biochemical differences in the exhalation of subjects with diagnosed cancer and subjects with no known cancer.
- Bladder cancer and prostate cancer, by sniffing the urine of patients.
- Colorectal cancer, by sniffing patients' exhaled breathing and their stool samples.
- Ovarian tumors, by sniffing patient tumor samples and blood samples.
- Cervical cancer, by sniffing patient biopsy samples.
