Can Dogs Detect Cancer? Discover How Dogs Are Trained to Sniff Out Cancer

Editor’s Note: This is the 4th in an occasional series of articles about various types of working dogs in the United States. Previously, we spotlighted bomb-sniffing dogs, guide dogs and service dogs for children with autism. Today, we highlight dogs that can detect cancer.

Can Dogs Detect Cancer with Their Incredible Sense of Smell?

Dogs have amazing noses. Their sense of smell is up to 100,000 times greater than human ability. To our puny 5 million scent receptors in the nose, dogs have 300 million. Dogs have around 40 percent more of their brain devoted to the sense of smell than humans do.

In other words, can dogs detect cancer? Absolutely, as they are super smellers.

• Dogs can sniff out drugs and bombs in suitcases, packages, and under cars.
• Search and rescue dogs can follow the footsteps of a missing hiker, even though dozens of people may have passed more recently.
• Dogs can find survivors in earthquakes and bodies at the bottom of a lake.

Maybe you’ve heard some of the stories circulating about dogs saving their humans' lives by sniffing and pawing at a spot on their body that turned out to be cancer. Scientists have been paying attention — and so have dog trainers.

A World of Smells: Can Dogs Detect Cancer?

Dina Zaphiris, a dog trainer and handler, is at the forefront of research on dogs detecting cancer. She founded In Situ Foundation, dedicated to training dogs to detect early-stage cancer by sniffing it out.

“The nose is a dog’s primary sense,” says Zaphiris.

• Dogs' whole world is based on smell. As humans, our primary sense is vision. If we look out a window, we can see thousands of things, but a dog can actually smell all those things.
• “If you related a dog’s sense of smell to human vision, what you and I can see across the yard, a dog can see from California all the way to New York," she says. "Dogs have been proven to detect odor at a part per trillion. There's no analogy. We are clumsy smellers.”

In 2003, a group of scientists asked Zaphiris to train dogs to smell cancer. “If you give me the substance, I can do that,” she said. Surprisingly, the samples turned out to be exhaled breath collected in tubes and frozen. She explains: “We don't train on tissue or tumors” -- the goal is to catch the cancer as early as possible, before there’s a detectable tumor.

Training Dogs to Make a Difference

The dogs were trained on hundreds of samples from cancer patients versus hundreds of samples from healthy patients. They were able to pick the cancer samples from the healthy samples because cancer is metabolized in the body very differently, and dogs can smell that difference.

Zaphiris trained a team of 5 dogs to detect early-stage lung and breast cancer in exhaled breath. The study was published in a medical journal, which sparked global interest and numerous replication studies. Zaphiris became a pioneer in the emerging field of cancer-detecting dogs.

• Zaphiris has trained more than 50 dogs to sniff out cancer in the past 13 years.
• “Every time we do a study, we don't use the same group of dogs. The scientists want to show replicability. They want to show that this can be done with any dog and different groups of dogs on different types of cancer.”

She looks for dogs with a strong play drive. “If they love the ball and played a few hiding games with me, they may make the team,” Zaphiris says. Learn more about dogs with a strong play drive.

For several studies, she used local dogs from the community. People would drop them off in the morning and pick them up at the end of the day. The dogs loved it. “That model becomes a very politically green and correct model for how a detection facility can run. People can get certified with their own dogs,” she says.

Accuracy and False Positives in Canine Cancer Detection

Accuracy levels for lung and breast cancer detection by dogs were 99 percent accurate, and 88 percent accurate for early detection of breast cancer. The overall specificity was 99 percent, meaning almost no false positives. “And that's huge,” Zaphiris says, “because one of the main problems with cancer is that everybody is getting false positives.”

• The PSA test for prostate cancer gives up to 85 percent false positives. That means 85 out of 100 men with elevated PSA levels are told they have cancer when they actually don't.
• False positives on mammograms resulting in additional testing can raise the cancer risk. According to Breastcancer.org, the 10-year risk of invasive breast cancer was “39 percent higher in women with false-positive results with a recommendation for more imaging.”

The problem with cancer testing is that there is no specific blood test for cancer, or else we would all get one every year. There are signs in the blood that may indicate cancer, such as a CA 125 (a protein called cancer antigen), but there are also thousands of other reasons for an elevated reading. By the time you have a tumor large enough for a biopsy, you already have cancer.

“The test is not specific enough,” says Zaphiris. “Dogs don't have that problem. If the dogs smell cancer, then you have cancer.”

New Research Can Help Save Lives

In 2003, In Situ collaborated with scientists on a lung and breast cancer study and, in 2012, an ovarian cancer study on exhaled breath samples. In all cases, “the dogs were very, very accurate,” says Zaphiris.

• She trains the dogs on early-stage cancer samples, which can also be saliva, urine, or plasma. “The dogs can find cancer before the machine can,” she says.
• The dogs are now being trained to detect specific types of cancer rather than just alerting for all cancers.

The current study is funded by the Department of Otolaryngology at UC Davis, focusing on detecting upper thoracic cancer in saliva. Dr. Hilary A. Brodie and Dr. Peter Belafsky are leading this initiative.

With UC Davis as a partner, In Situ has proposed a Center of Canine Excellence dedicated to ongoing research, protocol development, and training of cancer-detecting dogs and their handlers.

The American Cancer Society predicts nearly 1.7 million new cancer cases diagnosed and 600,000 cancer deaths in the United States this year. Maybe dogs can change that number and save our lives.

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