The researchers say using dogs to diagnose the disease could provide an alternative to the current blood test for prostate-specific antigen (PSA), which can give false results in men who do not have prostate cancer.
The team, led by the Humanitas Clinical and Research Center in Milan, Italy, collected urine samples from 362 men diagnosed with prostate cancer at different stages of the disease. They also took samples from 418 men and 122 women who were either healthy, had a different type of cancer, or had another health condition.
They then trained two 3-year-old female German shepherds to sniff out specific volatile organic compounds in urine associated with prostate cancer. Both the dogs, Zoe and Liu, had previously been trained in bomb detection work with the Italian armed forces.
After the dogs were retrained, they were tested using batches of 6 urine samples from the men with prostate cancer, positioned at random among those from others.
One dog correctly identified all of the prostate cancer urine samples and misidentified only 7 of the non-prostate cancer samples, or 1.3%.
The second dog correctly identified 98.6% of the prostate cancer urine samples and misidentified 13 of the non-prostate cancer samples, or 3.6%.
The researchers say the study, published in the Journal of Urology, demonstrates that a rigorously trained dog could sniff out prostate cancer samples with high accuracy. But they say that more tests are needed to see how well the dogs perform when faced with urine samples collected from men who are being examined for possible prostate cancer.
The findings back up tests carried out by the British charity Medical Detection Dogs. Its chief executive, Claire Guest, describes the study as "very significant."
The traditional PSA test, she says, although valuable, falsely finds cancer in 3 out of 4 cases. This means 75% of men who take the PSA test and receive a result of "cancer" have to take more tests to find out they don't have it.
"Moreover, the detection dogs provide an alternative solution that yields consistently accurate results," she days. "If our detection dogs were a machine, there would be huge demand for them. Dogs can pick up a scent in a dilution of one to a thousand parts. Their superior smelling power [is] well known."
Guest says there has been a lot of reluctance to allow dogs to be used for diagnosing diseases, based partly on the belief that animals would have to be brought into hospitals. But no patient-animal contact is needed for diagnosis, she says.
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