Numerous studies and a clinical trial have been conducted using dog To analyze samples from cancer patients, including urine samples, with the aim of evaluating if they could be used as early diagnosis method. This interest of the world of research for diagnostic capacity of the canine smell He was born in 1989when a British woman discovered she had a melanomaa dangerous skin tumor, after her dog had repeatedly sniffed a mole on her thigh. Two dermatologists published a report of this event on the famous scientific journal Lancet. However, despite some promising results, i traditional diagnostic methods remain nowadays more reliablemaking the presence of a dog in a clinic unnecessary.
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The sense of smell in dogs and the smell of cancer
The olfactory skills of the dogs are far superior to the human ones: while we have just 5 million olfactory receptors located on a relatively small area, the dogs have on average beyond 220 million, Distributed on a much more extensive area, and the olfactory lobes of their brain are more developed than ours. The sense of smell is not only at the basis of their survival skills, but also of social interaction: like many mammals dogs also have a special chamber, the vomeronasal organ, appointed to recognition smell associated with individuals or emotional states (In humans, this chamber is very narrow and is in all respects a vestigial organ).
For this reason, dogs are used in anti -drug operations during customs checks, such as hounds in the search for people who have disappeared or on the run, or to identify the presence of survivors under the rubble. It is therefore not surprising that we have tried to use them even in the clinical field, for the diagnosis of diseases including cancer. In fact, cancer cells, having a metabolism different from healthy ones, can produce a series of volatile compounds From the characteristic smell, which would go unnoticed for us, but that a dog would be theoretically able to perceive.
The results of diagnostic studies
From 2004 onwards, several double -blind scientific studies were conducted in which dogs came trainedusually through a reward system, to recognize samples from people with cancer and distinguish them from those from healthy people. The accuracy of the olfactory diagnosis varies from the case in case: just to mention some examples, the dogs have been able to identify with the smell the presence of bladder cancer (41% of accuracy), breast (84% of accuracy) or lung (80%). Between 2015 and 2020, the English national health system, in collaboration with the Medical Detection Dogs, a foundation that deals with the training of diagnostic dogs, has conducted a clinical trial To check if dogs could be trained to reveal prostate cancer, annusing Urine samples. Dogs identified the positive champions in 94% cases, and negative ones in the88%but the trial also highlighted difficulties in finding candidates who respond well to training.
Some percentages that bode well, but which still do not reach those obtained with traditional and simpler diagnostic methods. Also, nowadays, i volatile compounds of cancer they remain elusive: even if dogs know how to distinguish between a healthy champion and a sick one, The specific combination of smells has not yet been identified univocally associated with the presence of cancer.
Because dogs are not used to diagnose cancer
Although some results of these studies are comparable to those of traditional diagnostic methods, the use of dogs in the clinical field still remains Little practical compared to alternatives. Train a dog so that it is able to identify specific samples from the smell requires time e resourceand often also the presence of a trainer during the exam. The samples must however be taken from patients: To avoid influencing their reaction, dogs do not come into contact with patients, but sniff their isolated samples through special dispensers. These same samples could simply be analyzed with traditional laboratory techniques already able to identify the presence of tumors in a reliable way.
And it should always be kept in mind that even the best trained dogs are not automotive, but animals with their own personality and emotional state. Dogs love engaging situations in which the positive reinforcement is constant, e smell thousands of samples per dayonly some of which would be positive, it would be difficult and tiring for them, and would compromise their accuracy.
The adoption of dogs “sniffed” in the clinical field remains far away, yet their extraordinary olfactory skills have however been useful to us: it is thanks to them that we realized that cancer can be diagnosed with smells. This discovery could lead, in the future, to the development of “electronic noses“That reveal cancer and other diseases through volatile compounds, and without the presence of dogs in flesh and blood during the examination.
For this reason theAIRCItalian Association for Cancer Research, advises the same as contact a doctor If your dog insistently sniffs a part of the body: although less reliable of traditional diagnosis, it may still have perceived something that is better to have examined properly.
