Dogs Detecting Cancer

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Dogs have an immeasurable desire to serve, and they do so very humbly, asking for little in return. All across the globe, dogs have learned to help the blind see and the deaf hear, and out in California, there is a new kind of pup sniffing its way into the pack of service dogs. 

The Pine Street Foundation, a nonprofit cancer research group in San Anselmo, Calif., has trained five dogs to sniff out cancer with incredible accuracy. It’s known that a dog’s sense of smell is far superior to that of humans, but Pine Street’s research has taken it to a new level.

The Pine Street team started looking at alternative detective methods after a 1989 report about a dog who spent an inordinate amount of attention sniffing a skin spot on a female; after clinical examination, it turned out to be a malignant melanoma.

With curiosity high, foundation staff began reading into other reports of dogs detecting disease by smelling skin, bodily waste, removed tumors, and even exhaled breath. After extensive research, Pine Street decided to stick its nose into the biochemical markers that people release while breathing.

Dr. Michael McCulloch and the Pine Street team took breath samples from 55 patients with lung cancer, 31 patients with breast cancer, and 83 control subjects with no prior cancer history. Then, it selected five dogs to undergo training: three Labrador retrievers and two Portuguese water dogs.

Using clicker training, an operant conditioning method that uses a clicker to indicate success followed by a food reward, the dogs were successfully trained in two to three week’s time. Pine Street Foundation then conducted a series of single-blind and double-blind experiments to test their training.

The dogs would enter a room with five containers, one with a cancer patient breath sample and the other four containers with controlled samples of patients with no prior cancer history. Sitting by a specific container meant that the dog had picked up a cancer scent. Upon completion, the results were astounding.

The dogs were able to sniff out the lung cancer patient samples with 99 percent accuracy and breast cancer patient samples with 88 percent accuracy. A very low number of false-negatives appeared, too, as the dogs sat by healthy samples only four times and did not sit 708 times.

The results from the Pine Street Foundation’s study intrigued other groups and clinics to test their methods and accuracy. They are finding very similar conclusions.

“We’re actually now engaged in a project where we are assisting multiple other teams around the clinic who are doing this kind of work with the dogs,” McCulloch said. “We’re providing leadership and guidance for those teams. That’s where you really start to see that the method actually works. When you see the method being replicated, that’s when you start to know that it really has validity.”

Concerns have been raised, though, regarding nonmalignant inflammatory conditions, smoking, and what the patient ate before providing a breath sample and how that affects outcome. The Pine Street Foundation recognizes these concerns, but offers good news.

“There were findings that the dogs were actually able to really be quite discerning in separating out feeds from other things, like smoking,” McCulloch said. “And that’s wonderful—the dogs knowing what they’re supposed to be targeting.”

The Pine Street Foundation’s research is moving toward the development of an “electronic nose”—one that can detect the specific biomarkers in exhaled breath.

“Well, since our first paper was published, there are now dozens of different teams across the planet that are doing that kind of dedicated chemical analysis work,” McCulloch said. “So, it’s quite exciting to see that happening. It’s not going to be one compound, but rather a mixture of compounds, a panel of them.”

The success and continuation of Pine Street’s research could provide a medical breakthrough for screening processes. Instead of using radiation or surgical biopsies, our four-legged friends could provide their service sooner than anticipated.

“I’m going to anticipate that within the next five years, you’re going to see results from screening studies,” McCulloch said. “That’s where I think the benefit is really going to be—using the dogs as a low-cost screening method.”

This research proves once again that the benefits dogs offer to mankind are limitless. 

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