Can Dogs Really Detect Malignancy? This Study Proves It

Analysis by Dr. Karen Shaw Becker

dog sniffs tumor

Story at-a-glance -

  • In one of the latest studies on canine cancer detection, beagles were able to identify lung cancer by sniffing blood samples with about 97% accuracy
  • Four beagles were trained to use scent to distinguish blood samples from people with lung cancer from blood samples from people without cancer
  • Three of the four dogs correctly identified the cancer samples with a striking accuracy rate
  • Dogs have been trained to detect both specific cancers as well as “general cancer scent;” to date, cancer-sniffing dogs have detected scents associated with breast, lung, prostate, colorectal, thyroid, melanoma, lymphoma, renal and transitional cell carcinoma cancers
  • Cancer screening via canines is not legal in the U.S. unless it’s part of a clinical trial, but anecdotal reports exist of pet dogs alerting their owners of cancer

Dogs have extraordinary noses and can use their phenomenal sense of smell to help humans diagnose cancer. In one of the latest studies on canine cancer detection, beagles were able to identify lung cancer by sniffing blood samples with about 97% accuracy1 — an impressive feat and one that could make earlier cancer detection a possibility.

Study author Heather Junqueira, lead researcher at BioScentDx, a company using canine scent detection to develop cancer scent screenings, said in a news release, "Although there is currently no cure for cancer, early detection offers the best hope of survival. A highly sensitive test for detecting cancer could potentially save thousands of lives and change the way the disease is treated."2

Dogs Detect Cancer by Sniffing Blood Samples

During the first phase of the study, four beagles were trained to use scent to distinguish blood samples from people with lung cancer from blood samples from people without cancer. The researchers used a form of operant conditioning known as clicker training to teach the dogs.

With clicker training, when the dog does the desired behavior, a "click" sound is made, which lets the dog know he's on the right track. Three of the four dogs correctly identified the cancer samples with a striking accuracy rate of about 97%. Specifically, the results showed accuracy with "a sensitivity of 96.7%, specificity of 97.5%, positive predictive value (PPV) of 90.6% and negative predictive value (NPV) of 99.2%."3

The fourth dog, Snuggles, "was unmotivated to perform during training," according to the researchers, and as a result scored somewhat lower on accuracy than the other three dogs, coming in with 80% specificity and 60% sensitivity. Still, the study was a success, further supporting the usefulness of dogs in detecting cancer biomarkers.

"This study paves the way for a larger scale research project designed to explore the use of canine scent detection as a tool for detecting cancer biomarkers, ultimately leading to their identification," the researchers noted.4

BioScentDx is also involved in other research, including a breast cancer study determining whether trained cancer-sniffing dogs can detect cancer from breath samples from breast cancer patients.5 They're also working on isolating the biologic compounds that the dogs detect, which could pave the way for screening tests based on those compounds.6

Dogs Sniff Out Ovarian and Breast Cancers

In addition to lung cancer, past research found dogs were also capable of detecting cancer odor in the blood of ovarian cancer patients, not only at the time of first diagnosis but also at follow-up three and six months later. The dogs indicated positive samples in three of 10 patients at follow-up, and all three of them had recurrences.7

In Situ Foundation is also working on scientifically training dogs to detect early-stage cancer in humans and has partnered with the University of California-Davis to develop cancer detection dogs that will offer screenings to the public. In Situ, which trains only animals from shelters and rescues, who don't have homes, added:8

"Dogs have a high sensitivity and specificity, which means that dogs do not give the high false positive rates that modern day screenings give. False positives cause unnecessary biopsies, treatment, and worry.

In 2006, our study which was published in the Journal of Integrative Cancer Therapies,9 a medical journal, our dogs were proven at 99% sensitivity in the early detection of lung cancer, and 88% sensitive in the early detection of breast cancer. This is more accurate than a needle biopsy."

BioScentDx states that they have dogs trained to detect both specific cancers as well as "general cancer scent," as many cancers share a common scent. To date, their cancer-sniffing dogs have detected scents associated with breast, lung, prostate, colorectal, thyroid, melanoma, lymphoma, renal and transitional cell carcinoma cancers.10

Can You Be Screened by a Cancer-Sniffing Dog?

Currently, cancer screening via canines is not legal in the U.S. unless it's part of a clinical trial. BioScentDx sells screening kits, which state that by purchasing a kit, "you will be participating in a research study that will help further grow awareness and broaden the uses for canine scent detection in medicine."11

CancerDogs is also running firefighter cancer screening trials to get firefighters, who are at increased risk for cancer, regular cancer screenings. As of January 2018, 30,000 firefighters have been tested as part of CancerDogs' Firefighter Cancer Screening Trials.12

Although the screening is considered experimental and not a replacement for standard medical care, the hope is that dogs can help the firefighters detect cancer earlier, leading to more successful treatment. Ultimately, it's hoped that dogs may one day be able to detect cancer in the general public as well.

Further, it's not only specially trained dogs that may be able to sniff out cancer. Private pet owners have also reported that their dogs have alerted them to cancer. In 1989, researchers published a case report of a dog who sniffed a lesion on his owner's thigh, and the lesion turned out to be melanoma.13

In 2018, a Wisconsin resident also indicated her Siberian Husky Sierra successfully alerted her to ovarian cancer — not one but three times.14 With the scientific backing and anecdotal reports growing, if your dog seems unusually obsessed with smelling a certain part of your body, your breath or a spot on your skin, it may be worth paying attention.