Moist Nose Shows Promise in Tracking Down Cancers
By DONALD G. McNEIL Jr.
Published: September 28, 2004
British researchers have trained dogs to detect bladder cancer by sniffing human urine, opening up the possibility that dogs - or electronic noses modeled on their snouts - may one day be used to detect the disease.
The study, published in the British medical journal BMJ on Saturday, is the first to demonstrate scientifically that dogs can detect cancer through smell, its authors said.
Meanwhile, other research teams, at institutions from Cambridge University to Florida State, are testing dogs' ability to detect lung, breast and liver cancer in breath; prostate cancer in urine; and melanoma on skin.
The study, done at Amersham Hospital in Buckinghamshire, England, was small; six dogs sniffed at 54 urine samples after weeks of training.
As a group, they were only about 41 percent accurate. That is far below what is considered acceptable on most medical tests, but the idea is in its infancy.
Dogs will not, of course, replace X-rays, C.T. scans, fiber-optic scopes, mammograms, Pap smears and other cancer screens. But some expensive and invasive tests are done only after symptoms are found - like blood in the urine of chemical workers, who are at high risk of bladder cancer.
Also, without a biopsy, most tests cannot tell a tumor from a benign lump, as dogs apparently can.
Dog tests might eventually be cheap and work early, and they also might be useful in poor countries, scientists said.
The dogs - three cocker spaniels, a Labrador, a papillon and a mongrel - were lent to the researchers by a school training them to help the deaf. Most breeds have equally keen senses of smell, scientists say, and it is only temperament that, for example, makes bloodhounds better trackers.
Dr. Wallace Sampson, the editor of The Scientific Review of Alternative Medicine, which questions non-Western medicine and quackery, said he had previously laughed off the idea of cancer-sniffing dogs and that he was "still skeptical, but less than I was at first."
Dr. Sampson, who is also a retired professor of oncology at Stanford, said it was "chemically and biologically possible" that tumors gave off enough chemicals for dogs to smell, but he wanted further tests that would, for example, control for smokers, who are at high risk for bladder cancer and also have volatile tobacco chemicals in their urine.
Dr. Jim Walker, director of the Sensory Research Institute at Florida State University, said he was disappointed at the 41 percent success rate, which he said suggested that the dogs had not been trained enough.
"I hypothesize that dogs are phenomenally better than that," he said, adding that they will be useful only if it is shown that they can catch tumors earlier than doctors can.
In an intriguing side note to the British study, all six of the dogs detected cancer in the urine of a man who was thought to be cancer-free and was used as a control. When he was tested further, he was found to have a kidney tumor, and his life was saved.
"As you can guess, we were cock-a-hoop about that," said Dr. John C. T. Church, a retired surgeon who was the study's lead author.
Two of the spaniels were right five out of nine times. The mongrel and the Labrador, sniffing only dried samples, were right one and three times, respectively.
Dr. Church, a dog fancier, said he was inspired by a 1989 anecdotal report in The Lancet, another British medical journal, about a border collie-Doberman mix that kept nosing a mole on its owner's leg and even tried to nip it off. When removed, the mole turned out to be malignant.
Gas chromatography studies have shown that some tumors exude minute amounts of formaldehyde, alkanes and benzene derivatives not found in healthy tissue.
Dr. Walker's institute has done experiments showing that dogs can detect chemicals at one ten-thousandth to one hundred-thousandth the concentrations that humans can, while ignoring other odors.
Historically, doctors have used smell to make some diagnoses. Hippocrates described the fruity odor of diabetes in the breath and the musty odor of liver disease. In China, The Yellow Emperor's Classic of Internal Medicine counseled diagnosing lung infections by having patients spit into a fire; bacteria-laden sputum smells putrid.
Although the British study claims to be the most rigorously validated and is the first to be published in a major medical journal, other individual dogs have been trained to recognize cancers.
The leader of the pack was George, a schnauzer in Tallahassee, Fla. Originally a police bomb sniffer, he was retrained in 1993 to find test tubes with cancer cells, then encouraged to sniff humans lying on a low table and to place his paw on tumors.
In a paper accepted by Applied Animal Behavior Science, Dr. Walker describes how George correctly found melanomas on six of seven patients. (In training, George, who died in 2000, succeeded 100 percent of the time in finding a surgically removed tumor taped under one of many bandages on healthy volunteers.)
Shing Ling, an apricot-colored poodle at the Pine Street Chinese Benevolent Association clinic in San Anselmo, Calif., was trained in 2000 to detect lung and breast tumors in the breath of cancer patients. She had a success rate "up in the 80's" in percentage, said Michael McCulloch, the research director. (The association's clinic does not reject chemotherapy, surgery or radiation for cancer, but adds other approaches like acupuncture and Chinese herbs.)
Shing Ling died of liver failure two years ago, but this summer, Mr. McCulloch oversaw a new study with five other dogs. In it, 88 untreated cancer patients breathed into cylinders of plastic wool, as did 88 healthy volunteers. The handlers who presented the cylinders to the dogs did not know which were which.
Mr. McCulloch declined to give the results before the study was published, but he said they were "way better than chance."
Veterinary science researchers at Cambridge University in England are seeking financing for a set of urine tests like the Amersham one, but for prostate cancer.
Various electronic noses are in different phases of testing on lung cancer patients. Some contain spectrometers, but one contains minuscule polymers that swell when exposed to vapors, much as the noses of dogs and humans do. Named for the owner of a famous schnoz, it is called Cyranose.
dimanche, octobre 31, 2004
This is mad cool.