Anyone whose best friend is a dog will tell you that our furry friends are pretty darn good at everything they set their minds to. It's certainly true that the number of practical ways in which pooches help people is nothing short of impressive. As well as that familiar domestic avalanche of loyalty and love, an army of dogs across the world is finding disaster survivors, helping the visually and physically challenged, thwarting drug smugglers, combating terrorists and guarding our public spaces. One of their newest roles, and one they seem ideally suited to, is helping detect medical conditions in humans. Though dogs' ability to sniff out cancer has proven successful in the past, a new study — and its star, Frankie the German Shepherd — shows how their highly developed sense of smell could help usher in a new non-invasive method of early diagnosis.
The study, which will be presented this week in San Diego to the annual meeting of the Endocrine Society, will outline how a "trained scent dog" was able to pick out — with 88.2 percent accuracy — the urine samples of patients with thyroid cancer. Frankie — a rescued male German Shepherd mix — was trained (or "imprinted") by Dr. Arny Ferrando of University of Arkansas for Medical Sciences (UAMS) to recognize the smell of cancer in thyroid tissue.
For the study, the dog was presented with urine samples provided by 34 patients during their first appointment at the thyroid clinic. These patients also had traditional biopsies, the results of which were unknown to the staff handling Frankie and recording his responses — lying down for a positive result and turning away for a negative. Despite this blind test, Frankie correctly "diagnosed" 30 out of 34 patients — almost 9 out of 10 overall. According to Dr. Ferrando, "Frankie is the first dog trained to differentiate benign thyroid disease from thyroid cancer by smelling a person's urine."
According to Animal Planet, a 2004 study in England published in the British Journal of Medicine showed how dogs could be trained to detect bladder cancer from urine with a 41 percent success rate. Though encouraging, the research clearly had a way to go. Frankie's results, then, are exciting because they are so high. The study's senior investigator, Dr. Donald Bodenner, who is chief of endocrine oncology at UAMS, says Frankie's figures are only just short of those obtained from fine-needle aspiration biopsy, the way thyroid nodules are usually tested for cancer.
These results could be highly significant for patient treatment in the future. "Current diagnostic procedures for thyroid cancer often yield uncertain results, leading to recurrent medical procedures and a large number of thyroid surgeries performed unnecessarily," says Bodenner. Previously, dogs have been able to sniff out various cancers, including prostate and ovarian cases, from breath or body odor but biopsy has always been required to confirm. This method, as well as being fast and inexpensive, is non-invasive.
Dogs have an incredibly acute sense of smell. Even the least sensitive of them has at least 10 times more smell receptors than humans do. We have around 5 million smell receptors to help us navigate the world; a German Shepherd like Frankie has around 225 million. This means, says Animal Planet, that his sense of smell is around "one million times greater" than ours.
Within the dog's nose are so-called "turbinate bones" — scrolled spaces made up of spongy, moveable cartilage and ciliated epithelial cells that act as sensory receptors. The particular shape of these bones provides significantly more odor-sensitive inner surface than is present in humans. We only have around one square inch whereas dogs can have between 7 and 60 square inches. Coupled with a significantly larger percentage of the brain given over to processing smell, incredibly, this means dogs can smell things up to 40 feet underground and human fingerprints that are a week old.
The hopes for future detection by dogs like Frankie are high. The American Cancer Society (ACS) estimates that there will be around 62,450 new cases of thyroid cancer in the U.S. this year — three quarters of which will be women — resulting in almost 2,000 deaths. The good news is that, thanks to procedures like thyroid ultrasound, the detection rate is also increasing. Ultrasound, says the ACS, "can detect small thyroid nodules that might not otherwise have been found in the past." The sensitivity of the noses of trained scent dogs means the detection rate could be pushed even higher.
Although Bodenner is not currently using dogs for clinical diagnosis, there is every hope, he says, that dogs "could be used by physicians to detect the presence of thyroid cancer at an early stage and to avoid surgery when unwarranted." The UAMS team's plan is to collaborate with Auburn University College of Veterinary Medicine in Arkansas to expand their research. Two of their bomb-sniffing dogs are to be retrained to sniff out thyroid cancer. Certainly, no one is ever going to accuse Frankie of being just a pretty face.