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Researchers have long suspected that man’s best friend has a special ability to sense when something is wrong with him. Now the first experiment to verify that scientifically has demonstrated that dogs are able to smell cancer. Experts say it’s unlikely that pooches will become practical partners in cancer detection anytime soon, but the results of the study, outlined in the September 25 British Medical Journal, are promising.

They show that when urine from patients with bladder cancer was set out among samples from healthy people or those with other diseases, the dogs — all ordinary pets — were able to identify the patients with cancer’s urine almost three times more often than would be expected by chance alone.

Dogged by communication issue

“The issue is not whether they can detect cancer, because clearly they can. The issue is whether you can set up a system whereby they can communicate with you. That requires further ingenuity,” says Tim Cole, a professor of medical statistics at Imperial College in London who was unconnected with the study and is the owner of a chocolate Labrador retriever.

David Neal, a bladder and prostate cancer surgeon at Cambridge University
in England, said it’s plausible that dogs might be able to pick up the scent of cancer because people with the disease shed abnormal proteins in their urine.

“I’m skeptical about whether it will be implementable, but scientifically it should be followed up,” says Neal, a spokesman for Cancer Research UK, Britain’s cancer society, who was not involved in the research. “It might be that the dogs are better than our current machines at picking up abnormal proteins in the urine. What are the dogs picking up? Can we get a machine that does the same?”

The nose knows

It is thought that a dog’s sense of smell is generally 10,000 to 100,000 times better than a human’s.

The experiment, conducted by researchers at Amersham Hospital in Buckinghamshire, England, and the organization Hearing Dogs for Deaf People, set out to prove whether dogs could be trained to detect cancer.

Six dogs — all pets of the trainers — were used in the study. They included three working strain cocker spaniels, one papillon, a Labrador, and a mongrel.

The trainers used urine from patients with bladder cancer, from people sick with unrelated diseases, and from healthy people to train the dogs over seven months to select the cancer-unique elements by process of elimination. They learned to ignore differences in the urine samples that were due to age, sex, infection, diet, and other factors.

Urine from 36 patients with bladder cancer and 108 comparison volunteers was used. Each dog had to sniff seven urine samples and lie down next to the one from a patient with bladder cancer. The test was repeated eight times for each dog, with new urine samples every time.

Spaniels stand out

Taken as a group, they correctly selected the right urine on 22 out of 54 occasions, giving an average success rate of 41%. By chance alone, you’d expect them to be accurate one-seventh, or 14%, of the time.

The two best dogs, Tangle and Biddy — both cocker spaniels — were right 56% of the time, according to trainer Andrew Cook.

One of the patients with cancer was identified correctly by all six dogs, whereas two other patients with cancer were consistently missed, indicating that perhaps the strength of the urine signal varies from person to person or according to severity of the disease.

Did dogs save a life?

Perhaps the most intriguing finding, though, was in a comparison patient whose urine was used during the training phase.

All the dogs unequivocally identified that urine as a cancer case, even though screening tests before the experiment had shown no cancer. Doctors conducted more detailed tests on the patient and found a life-threatening tumor in the right kidney.

Lisette Hilton is a freelance health care reporter, specializing in covering local, national, and worldwide news for nurses, pharmacists, physicians, and other allied health professionals.