It seems that new cancer breakthroughs are happening all the time. But in recent years, one particular discovery has caught the public’s imagination: cancer-sniffing dogs. Now, as Yvette Tan at Mashable reports, residents of a town in Japan with high rates of stomach cancer are participating in a trial to test the accuracy of these cancer-sniffing canines.

Related Content Cancer Is One Worry Elephants Can Feel Free to Forget

According to Tan, residents of Kaneyama, a town of 6,000 in the Yamagata Prefecture will send frozen urine samples to Nippon Medical School, located outside of Tokyo. There, highly trained detection dogs will sniff the samples for signs of cancer. It’s believed the dogs are able to detect specific odors cancer cells emit that humans are not able to detect.

“In our research so far, cancer detection dogs have been able to find [signs of] cancer with an accuracy of nearly 100 percent," Masao Miyashita, a professor at the medical school leading in the program tells Japan Today.

While the project and others like it are interesting, they have their critics. Using dogs isn't very cost effective, Cynthia Otto, director of the Penn Vet Working Dog Center at the University of Pennsylvania's School of Veterinary Medicine tells Sara Chodosh at Popular Science. The point of screening people for cancer is to do it quickly and cheaply in order to cover as many patients as possible. For the Japanese trial, training one of the dogs costs a whopping $45,000.

And dogs can have good days and bad days. They can’t tell their handlers why they might have made a mistake on a certain day, so it’s hard to adjust the training. “They have all of these influences that can throw them off, and we may not recognize it,” Otto tells Chodosh. “We don’t want to risk somebody’s life on that.”

Even so, the ability to sniff out cancer is impressive and intriguing. And researchers have continued to pursue the idea. A Quebec-based program called CancerDogs is screening some U.S. firefighters who typically have higher than normal cancer rates. A program in the U.K. called Medical Detection Dogs has participated in a study where dogs sniff out signs of prostate cancer. An initial study showed the dogs could detect prostate cancer in 93 percent of cases.

“Our dogs have higher rates of reliability than most of the existing tests. We know their sense of smell is extraordinary. They can detect parts per trillion —that’s the equivalent of one drop of blood in two Olympic-sized swimming pools,” Claire Guest, founder of Medical Detection Dogs tells the Press Association. “We should not be turning our backs on these highly sensitive bio-detectors just because they have furry coats.”

Even if the tests don’t lead to Doggy M.D.s roaming hospitals, Otto told Joshua A. Krisch at The New York Times in 2014 that the projects are worthwhile if they help isolate the compounds the dogs are detecting. That could lead to new nanotech sensors that could find cancers as well or even better than the pups.

But medical detection dogs seem to already have a place in medicine. Currently diabetes assist dogs alert their owners when they detect low blood sugar scents and seizure alert dogs are trained to help people with epilepsy. So perhaps, in the future, our furry friends can help sniff out cancer as well.