For men of a certain age, the prostate goes from a background to a foreground worry. The walnut-sized gland circles the neck of the male bladder, and when it starts causing problems, there can be a number of reasons. The most serious is cancer. To arrive at a definitive diagnosis requires a biopsy, which--like any surgery--comes with its own risks. And this is why the "false positive" rate matters: in order to make a decision to go ahead with a biopsy, a man needs to have a pretty good idea that it's needed. The more accurate the screening, the fewer unnecessary biopsies.
Prostate cancer is the second leading cause of cancer death in men in the developed world. Clinicians have sought 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.
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The researchers had trained the animals, Florin, a 4-year-old female Labrador, and Midas, a 7-year-old female wirehaired Hungarian vizsla, 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 Alan Partin, urologist-in-chief at Johns Hopkins Hospital.
“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, helped the researchers filter the more than 1,000 VOCs present in a typical urine sample down to those most beneficial for cancer diagnosis, Partin says.
The dogs performed their cancer detection roles well, Partin says. Both Florin and Midas identified five of seven urine samples from men with cancer, or 71.4% accuracy. Florin correctly identified 16 of the 21 non-aggressive or no cancer samples (76.2%), and Midas picked out 14 (66.7%).
In another UK National Health Service (NHS) preliminary study, trained dogs were able to sniff out prostate cancer 9 out of 10 times, making them a more accurate predictor than the standard (but controversial) Prostate-Specific Antigen (PSA) screening test, which has a high "false positive" rate.
When researchers combined the canine olfactory (smell) results 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.
It looks like we soon may be able to chalk up another win for the power of the canine nose.