Prostate cancer is one of the most common cancers among men and represents a major cause of mortality in developed countries. Today, its screening is based on several additional examinations, such as rectal examination, PSA measurement in the blood, MRI or even biopsies. But the PSA test, although used on a large scale, is not always sufficiently precise, which pushes researchers to develop new, more reliable diagnostic methods.
Among the most surprising avenues is olfactory screening by specially trained dogs, an area explored by clinical odorology. Thanks to their extremely developed sense of smell, these doggies would indeed be able to detect volatile organic compounds specific to prostate cancer in urine samples. A recent study carried out by Italian researchers showed that rigorous training allowed these dogs to achieve very high diagnostic accuracy.
Amazing precision
For this, the team of researchers led by the Dr Gianluigi Taverna conducted a double-blind experiment using standardized urine samples. Two female dogs German Shepherds 3 years old, Zoe And Liupreviously trained in the detection of explosives, underwent specific training for 5 months to recognize volatile organic compounds associated with prostate cancer. The tests then focused on the urine of 902 participants, including 362 men with prostate cancer at different stages and 540 healthy people or people suffering from other illnesses.
The results, published in the Journal of Urology*, are particularly impressive: the female dogs achieved a success rate of up to 98%, with very few errors (only 16 false positives and 4 false negatives). One of the 4-legged testers even correctly identified 100% of the positive samples!
How dogs spot cancer molecules
This canine screening method is based on a simple idea: when a tumor develops, it modifies the body's metabolism and leads to the production of specific volatile organic compounds (VOCs), eliminated in particular in the urine. However, thanks to their approximately 200 million olfactory cells – or around 40 times more than humans – dogs are capable of detecting minute traces of these molecules. After several months of rigorous training, sniffer dogs can learn to recognize a real “chemical signature” associated with prostate cancer.
Although the results obtained in this Italian study are particularly striking, the researchers nevertheless point out that it is above all a proof of concept and not a diagnostic tool ready for use in hospitals. Performance may vary depending on the dogs, training conditions or protocols used.
In any case, this work shows that canine sense of smell could, in the future, become a promising complementary tool for prostate cancer screening, even if additional studies remain necessary before large-scale use.
* Taverna G. et al., “Olfactory system of highly trained dogs detects prostate cancer in urine samples”, Journal of Urology, 2015 April;193(4):1382-7.