The Dog’s Nose in Prostate Cancer Detection
Puppies are born blind and deaf, and stay this way until approximately 14 days of age, so their lives depend on finding the mother’s nipple through smell. This early stimulation of olfactory organs allows them to reach adulthood with the ability to smell the equivalent of a tablespoon of coffee in 2 Olympic pools of water.
In the mid-17th century, monks in a hospice located in the Great Saint Bernard Pass, in the Italian Alps, used dogs in the rescue of lost mountaineers amidst snow and fog. Since then, humans have used dogs’ olfactory skills in a variety of activities, from searching for people, drugs, explosives, and endangered animal species for their conservation, to the detection of significant changes in our cells, alerting us to illnesses such as type 1 diabetes or cancer.
The high accuracy of trained dogs and its application in the diagnosis of several illnesses has been documented in the last few years, and we at Waybi Foundation and the Universidad Francisco Marroquín’s (UFM) School of Nutrition have wanted to make use of this attribute of the species to work together in a biodetection project consisting of the training of dogs who, through their sense of smell, can detect prostate cancer in urine samples.
The study started with two female dogs, Trixtan, a 7-year-old golden retriever, and Giselle, a 4-year-old Labrador retriever. The process of teaching dogs to detect the scent of prostate cancer in urine begins with a game. The scent was presented in a small container in the initial stages and paired with a reinforcer.
Once the association was clear, they had to discriminate between the container with the positive sample and empty containers, initiating the game of having to “search and find” in order to receive the reinforcement.
With the game rules established, Trixtan and Gisselle had to learn to play on another device, a “spider” with eight arms, in which control samples with similar scents were gradually added (urine samples of healthy people and with other pathologies like prostatitis and hyperplasia), until a proportion of one positive sample versus seven control samples was reached. The training is perceived by the dogs as a reinforcing game, where they show us the positive samples as they play
We are currently halfway through the research, and so far we’ve gotten very encouraging data: 97.3% sensibility (the dog’s ability to identify the positive sample) and 96.8% specificity (the proportion of negative samples correctly identified). During this time we’ve been perfecting our technique, and we are convinced that the next results will be even better. This project will help us detect prostate cancer in its early stages, in a way that is less invasive, more accessible and less expensive. This will facilitate access to treatment and recovery for people who live in Guatemala’s Interior, who often, due to lack of education and other resources, do not have easy access to diagnosis and later treatment.
These days there are many researchers striving to develop robotic noses as precise as a dog’s nose in the early detection of diseases, but so far they haven’t achieved it. As the inventor Andreas Mershin says, “Dogs are the earliest, least false positives, least false negatives, cheapest, fastest cancer detectors we have”.
(Translation: Natalia Durston, IAABC)
For over 10 years Raúl Maroto has coordinated animal-assisted therapy programs of applied behavior analysis and has collaborated in animal training and staff education of several Guatemalan zoos. He is currently participating in two studies on detection through canine sense of smell, and is the training coordinator of farm animals at Waybi Foundation in Guatemala.