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Dogs have been called man’s best friend because of their loyalty and protection, but now, thanks to Johns Hopkins Medicine researchers and an international team of collaborators, canines may provide an even greater service for their human male companions: prostate cancer screening.
Prostate cancer is the second leading cause of cancer death in men in the developed world. Clinicians have been seeking accurate and reliable noninvasive diagnostic tools to differentiate early stage, less dangerous, and more treatable stages of the disease from the aggressive, high-grade, and likely-to-spread forms. Standard blood tests for early detection, such as the prostate-specific antigen (PSA) test, often miss cancers in men whose PSA levels are within normal levels or overdiagnose men with clinically insignificant tumors or no cancer at all.
Recently, Alan Partin, M.D., Ph.D., urologist-in-chief at The Johns Hopkins Hospital and colleagues, along with collaborators from the United Kingdom, the Prostate Cancer Foundation and the Massachusetts Institute of Technology, have been researching a dog’s extremely sensitive sense of smell as a novel way to improve testing for prostate cancer.
In a small study published Feb. 17, 2021, in the journal PLOS ONE, the researchers had two dogs sniff samples of urine from men diagnosed with high-grade prostate cancer and from men without cancer. The animals, Florin, a 4-year-old female Labrador, and Midas, a 7-year-old female wirehaired Hungarian vizsla, had been trained to respond to cancer-related chemicals — known as volatile organic compounds (VOCs) — added to urine samples and not respond to ones without them.
“Besides PSA, other methods to detect prostate cancer make use of a molecular analyzer called a gas chromatography-mass spectrometer [GC-MS] to find specific VOCs or profiling bacterial population in a urine sample looking for species associated with cancer, but these have limitations,” says Partin. “We wondered if having the dogs detect the chemicals, combined with analysis by GC-MS, bacterial profiling, and an artificial intelligence [AI] neural network trained to emulate the canine cancer detection ability, could significantly improve the diagnosis of high-grade prostate cancer.”
Adding the AI analysis, says Partin, helped the researchers filter the more than 1,000 VOCs present in a typical urine sample down to those most beneficial for cancer diagnosis.
The dogs, says Partin, performed their cancer detection roles well. Both Florin and Midas identified five of seven urine samples from men with cancer, or 71.4% accuracy. Florin was able to correctly identify 16 of the 21 non-aggressive or no cancer samples (76.2%), while Midas was able to pick out 14 (66.7%).
When the canine olfactory (smell) results were combined with GC-MS, bacterial profiling, and AI analysis, the multisystem approach proved a more sensitive and more specific means of detecting lethal prostate cancer than any of the methods alone.