When it comes to detecting prostate cancer accurately and noninvasively, dogs may be ahead by a nose.
With near-perfect accuracy, rigorously trained German shepherds demonstrated that they were able to identify the presence of the disease by smelling volatile organic compounds released into urine by prostate tumors, according to the results of a study presented during the 2014 Annual Meeting of the American Urological Association (AUA) in Orlando, Florida.
While prostate-specific antigen (PSA) testing plus a first biopsy have an accuracy rate of about 30% in detecting prostate cancer, the dogs alone were accurate 98% of the time, a panel of researchers at the press conference said. The information conferred by dogs could represent a promising tool to be added to a typical detection nomogram that includes PSA values, free/total PSA ratio, Prostate Health Index, and other information, they said.
“The potential use of dogs for recognizing prostate cancer could reduce unnecessary prostate biopsies and pinpoint patients at high risk for prostate cancer,” said lead author Gianluigi Taverna, MD, chief of the Prostatic Disease Unit at Humanitas Research Hospital in Italy.
The study was conducted at that and other leading Italian institutions, including Humanitas Castellanza. In addition to Taverna, the research team included a doctor of veterinary medicine with a specialty in animal behavior, a biologist, and two dog handlers.
The study included 902 patients whose health status was known. They were divided into a prostate cancer group (n = 362), in which patients had prostate cancer ranging from very low-risk to metastatic, and a control group (n = 540) of healthy subjects not affected by neoplastic disease or prostatic tumor.
Two dogs carried out the testing in an environment free of olfactory interference. Dog one, Liu, boasted a 99% rate of accuracy, with sensitivity of 100% and specificity of 98%. Dog two, Zoe, had a 97% rate of accuracy, with sensitivity of 98.6% and specificity of 96.4%.
The dogs were able to detect prostate cancer at any stage, but could not discriminate between stages, Taverna said.
To detect cancer, the dogs were walked by trainers a couple of times around a small circular indoor course, stopping for a second or two at a time to sniff each of a half-dozen urine samples from different patients, which had been frozen and transported to their location. The dogs sat down when they smelled cancer.
“To the dogs, this is simple play, and when they play well, they get a ball,” Taverna said. “The handler does not know the location of the cancer, so the study is blind.”
To succeed, the animals, taught the detection process over 6 months, must be as highly trainable as explosive-sniffing dogs—“super dogs, the Ferrari of the dog,” Taverna said.
To keep the strategy as accurate as possible, trainers are responsible for spotting a dog that is not performing up to expected standards because it is tired, stressed, distracted, or ill, and giving the animal a rest, added the biologist in the group, Fabio Grizzi, PhD, also of Humanitas Research Hospital.
Now that the study has been completed, Taverna said, some questions remain: exactly what the dogs smell in the urine, whether it is one odor or a mixture, and whether the animals are picking up something secreted by cancer cells or by their microenvironment.
Investigators are also considering how dogs might be used in daily practice. One possibility is to decipher what the dogs are smelling in the urine—something Taverna now intends to study—and then create an “electronic nose” machine or gas chromatography method that can duplicate that ability, panelists said. However, the moderator of the discussion, Brian Stork, MD, a urologist with West Shore Urology in Michigan, noted that the olfactory system of a dog boasts a complexity that is “better than any machine.”
Part of the rationale for conducting the study was the understanding that dogs have a stronger sense of smell than humans, the AUA said in a press release. While humans have roughly five million olfactory cells in their noses, dogs have about 200 million. For years, law enforcement and the military have used dogs to help locate bombs and drugs, and in recent years, new findings have emerged to indicate that dogs are capable of detecting the onset of epileptic seizures as well as malignancies of the breast and lung, according to the press release.
The investigation presented Sunday follows a 2010 research study that demonstrated the ability of dogs to “sniff out” prostate cancer within a group of 33 patients, the AUA added.
“These data show [that] analysis of volatile organic compounds in urine is a promising approach to cancer detection,” Stork concluded. “The possibility of using dogs in identifying cancer is something most would never have considered possible a decade or two ago. It’s an interesting concept that ‘man’s best friend’ could help save your life.”