Dogs are often referred to as "man's best friend," and a new study brings further strength to this term after revealing how a rescue dog called Frankie was able to detect the presence of thyroid cancer in human urine samples with almost 90% accuracy.
According to the research team, from the University of Arkansas for Medical Sciences (UAMS) in Little Rock, Frankie - a male German Shepherd-mix - is the first dog that has been trained to differentiate benign thyroid disease and thyroid cancer by sniffing human urine samples.
Thyroid cancer is a cancer that begins in the thyroid gland, situated just below the thyroid cartilage in the front of the neck. Approximately 62,450 new cases of thyroid cancer will be diagnosed in the US this year, and around 1,950 Americans will die from the disease.
Unlike most other cancers, thyroid cancer is more common among younger adults, with almost 2 in 3 cases diagnosed in people under the age of 55.
Diagnostic techniques for thyroid cancer include fine-needle aspiration biopsy, which involves the patient having a thin needle inserted into the thyroid gland in order to obtain a tissue sample.
Senior investigator Dr. Donald Bodenner, chief of endocrine oncology at UAMS, says the diagnostic accuracy of canine scent detection is almost on par with that of fine-needle aspiration biopsy, but it would be an inexpensive and noninvasive alternative.
What is more, he notes many current methods for diagnosing thyroid cancer can be inaccurate, causing some patients to undergo needless surgery.
"Scent-trained canines could be used by physicians to detect the presence of thyroid cancer at an early stage and to avoid surgery when unwarranted," he adds.
Frankie trained to sniff out cancer in human urine samples
For their study, recently presented at The Endocrine Society's 97th Annual Meeting in San Diego, CA, Dr. Bodenner and colleagues obtained urine samples from 34 patients who attended the UAMS thyroid clinic.
All patients showed abnormalities in their thyroid nodules and went on to have biopsies and diagnostic surgery. Thyroid cancer was identified in 15 patients while 19 had benign thyroid disease.
Frankie - who the researchers say had been previously trained to recognize the smell of cancer in human thyroid tissue - was presented with the urine samples to sniff one at a time by a gloved dog handler.
While humans have around 5 million smell receptors, or olfactory cells, dogs possess around 200 million, making their sense of smell around a thousand times stronger than that of humans.
Frankie alerted the handler to a cancer-positive urine sample by lying down, while turning away from the urine sample alerted the handler to a benign status.
The authors note that the cancer status of each urine sample was unknown to both the dog handler and the study coordinator.
The handler also presented Frankie with urine samples with a known cancer status in between the study samples so the dog could be rewarded for achieving a correct answer.
30 out of 34 samples correctly identified with canine scent detection
On comparing Frankie's results with those of the final surgical pathology report for the samples, the team found the dog correctly identified the status of 30 out of 34 samples.
The sensitivity, or true-positive rate, of the canine scent detection came in at 86.7%, while specificity, or true-negative rate, was 89.5%. This means Frankie correctly identified a benign sample almost 9 in every 10 times.
The team notes that canine scent detection led to two false-negative and two false-positive results. The researchers now plan to expand their research by teaming up with Auburn University College of Veterinary Medicine, AL, who have agreed to assign two of its bomb-sniffing dogs to thyroid cancer detection training.
This is not the first time Medical News Today have reported on the cancer-detection talent of dogs. In May 2014, a study by Italian researchers revealed how specially trained dogs were able to detect prostate cancer in urine samples with 98% accuracy.