The Detection Dogs Who Can Smell Early Disease

hen Max, a 10-year-old Border Collie mix started to show a sad and apathetic mood that contrasted with his usual happy playfulness, his owner, a British woman named Maureen Burns, thought that Max was approaching the end of his life.

Max kept nudging his owner’s right breast and smelling her breath with insistence several times a day. The dog’s odd behavior prompted Maureen to check her breasts, and she discovered a small lump. A mammogram came out negative, but she persuaded her doctors to perform a biopsy. The lump proved out to be malignant and was surgically removed, followed by radiation treatment. After the surgery, Max returned to being the happy and playful dog that he was before and lived another two years.

As early as 1989, doctors at King's College Hospital in London wrote in the medical research publication The Lancet about a British woman whose dog persisted in smelling a mole on her thigh several times a day. The mole turned out to be an early-stage undetected malignant melanoma, which removal may have saved the woman’s life.

Since 2006, when the first double-blind studies were published, there is sound scientific evidence that dogs are able to smell the presence of cancerous cells through human breath or urine samples, or directly on the person, with an accuracy exceeding 90%. (double-blind testing means that neither the dogs nor the handlers know which samples are cancerous)

A dog's nose

Dogs have smell receptors up to 100,000 times more accurate than humans. They allow dogs to selectively detect a vast range of complex odor compounds that humans cannot detect. More than a third of a dog’s brain functions are assigned to smell-related operations, while in comparison, a human brain assigns a mere 5%.

A dog can identify chemical traces in the range of one part per trillion. That means being able to detect one drop of blood in five Olympic-sized swimming pools. 

Beagles and hounds have higher olfactory sensitivity than other breeds, but Labrador retrievers and breeds from the sporting group are also very capable and easier to train.

Bio-detection and medical assistance dogs

People most commonly associate detection dogs with illegal drugs and explosives, but trained alert dogs are now frequently used for the medical assistance of epileptic and diabetic patients, and bio-detection dogs have been trained since 2003 to reliably detect volatile organic compounds (VOCs) that are altered in the early stages of malignant cancers.

A leading British nonprofit organization since 2008, Medical Detection Dogs, is currently running a large clinical trial on 3,000 patients for the National Health Service, to establish the accuracy of dogs in the early detection of prostate cancer from urine samples. Claire Guest, the CEO, and founder of Medical Detection Dogs, caught her breast cancer in 2009 when she was 46, thanks to Daisy, her fox red Labrador who detected a small cyst that proved to have underlying cancer cells undetectable with a mammogram. 

A COVID-19 Bio detection project is also currently underway. Professor Steve Lindsay, from Durham University, said bio-detection dogs could be used at airports and public places to rapidly identify people carrying the virus and help prevent the re-emergence of the disease.

Dogs4Diabetics is a U.S. organization founded in 2004 that researches, trains, and places medical assistance alert dogs with insulin-dependent diabetics. A dog can detect the onset of a hypoglycemic attack as early as 20 minutes before the first symptoms appear, even when the dog is in a different room from the patient. The dog alerts the patient to check her insulin-levels, and can prevent a life-threatening diabetic coma from occurring.

How reliable and accurate are dogs at detecting cancer?

A 2019 study by BioScentDx in Florida using Beagles has shown that dogs can use their highly evolved sense of smell to pick out blood samples from people with malignant lung cancer with 97.5% accuracy. The results could lead to new cancer-screening approaches that are inexpensive and accurate without being invasive.

The Humanitas Research Hospital in Milan took urine samples from 320 men with prostate cancer and 357 without it. The men with cancer had different stages of the disease from low-risk to high-risk tumors. The dogs used for this study had an accuracy rate of 98%, which the team reported to the annual meeting of the American Urological Association.

An expert in melanomas, Dr. Cognetta of Tallahassee, studied whether dogs could detect skin cancer. The dog used in the study was able to detect melanoma 99% of the time.

In a research study conducted by the Pine Street Foundation, breath samples of 31 breast cancer patients, 55 lung cancer patients, and 83 healthy people were presented to five trained dogs (3 Labradors and 2 Portuguese water dogs). The dogs were able to detect or rule out breast and lung cancer, at all stages of the disease, with 90% accuracy.

How are bio-detection dogs trained?

Training methodologies vary, but in principle the reward-based techniques used are similar to the ones used when training police dogs in explosives and narcotics detection. Trained dogs can either smell target odors directly on people, or detect odor samples from a number of ventilated containers placed in a laboratory setting.

Dina Zaphiris, the founder of the nonprofit cancer-dog training organization In Situ Foundation in California, developed one of the first protocols for training cancer-detecting dogs. Having trained 52 dogs, she now trains dog handlers from around the world. Each In Situ dog trains for up to eight months, smelling samples of breath, plasma, urine, and saliva collected by doctors and sent to the foundation. After smelling more than 300 unique samples, dogs can distinguish between a healthy sample and a cancerous one.

What does it mean for early cancer screening?

Since peer-reviewed research on the subject of using dogs for bio-detection has been publicly available since 2004 and has shown such promising results, we might wonder why these techniques are not more widely used and accepted.

British member of Parliament Iain Duncan Smith asked the Health Secretary Jeremy Hunt why dogs are not yet widely used for cancer screenings in the National Health system, despite years of research and clinical evidence demonstrating their accuracy, cost-effectiveness and reliability. The answer suggest some degree of resistance and skepticism from the medical community, and a lack of political support and public funding because of the unorthodoxy of the methods. Ironically, the Health Secretary admitted that if the same results were obtained through a laboratory equipped with state-of-the-art technology—and without the word “dogs” in the name—the attitude would probably be very different.

What is the future of bio-detection dogs?

Medical experts unanimously agree that early detection is the most important factor in surviving cancer.

Researchers are confident that in the near future, dogs will be able to help scientists and medical staff develop faster and cheaper ways to detect diseases, such as cancers, viruses, neurological diseases and bacterial infections much earlier than is currently possible.

Researchers believe trained dogs will become integrated directly into patient care, while other researchers recommend the skills of the cancer-detecting dogs be confined to the laboratories, where the gas chromatographs could be used to isolate the specific compounds that are identified by the dogs. Some scientists also believe that the development of electronic systems—called “electronic noses”—will help in the detection of early cancers. All of this will be possible in a non-invasive way and at a very low-cost.

Many organizations work to help advance research in canine bio-detection and medical assistance programs. It is worth remembering that since most of these organizations are nonprofit, they don’t receive public fundings and depend on private donations.