The Nose Knows
It is a weekday morning in the summer of 2002. Charles Gibson, the anchor of ABC's "Good Morning America," introduces Dr. Nancy Snyderman, the show's medical correspondent. She is in California at a traditional Chinese medicine clinic co-founded by Michael Broffman '75.
The camera pans to Broffman's apricot-colored poodle, Shing-ling. "You may be looking at a cutting edge tool in early cancer detection," Snyderman says. "Yes - it's the dog."
Broffman theorizes that cancer alters our chemical makeup and that the changes are detectable in the way our breath smells. No machine exists that can detect these subtle shifts. But Broffman and other adherents to his theory believe the canine nose, with its highly-refined olfactory capacity, can.
Back on camera, Shing-ling is presented with two canisters, each one fitted with a filter. A cancer patient has breathed into one filter, a healthy volunteer into the other.
"Find it Shing-ling," the dog's trainer commands. Shing-ling sniffs both canisters, then paws one. It was the cancer sample. Snyderman quotes the clinic's statistics, which say Shingling identifies the cancer sample 87 percent of the time. Then she adds, "Many doctors won't believe it until real evidence comes in." A skeptical Gibson asks, "Nancy, do you really think this is possible?"
In the year since Shing-ling's television debut, Broffman and his colleagues at the Pine Street Clinic have mounted the first major trial of their theory, using breath samples taken from 84 lung and breast cancer victims. When the results were tabulated, the dogs detected 91 percent of the lung cancer and 90 percent of breast cancer cases correctly, Broffman said. In the tests, the dogs had to choose from five samples.
He believes the dogs are detecting particular volatile organic compounds - gases containing the element carbon - that have been captured in the canister filter. Since human breath typically contains over 200 different volatile organic compounds, this is a tall order.
Some of these compounds are detectable by gas chromatography equipment, but the VOC's that make up the scent for cancer are beyond the reach of machines. Machines can only detect scents measured in parts per trillion. The cancer samples are believed to be in much lower concentrations - as low as 10 parts per quadrillion. Fortunately, canine noses are quite elaborate; they are believed to have about 200 million scentreceiving cells, which allow them to detect samples 1,000 times more diluted than can be read by machines.
The trick is to get the dogs to focus on the particular compounds that might be present in a sample. And some medical experts don't think this is possible; even if cancer does change breath chemistry, they say, the dogs couldn't distinguish the scent of cancer from all the other smells.
Using the breath to diagnose disease is an ancient tradition in both eastern and western medicine. Many diseases cause a change in breath smell discernible even to relatively unrefined human noses.
In China, the Yellow Emperor's Classic of Internal Medicine (third century BC) described a fruity odor used to diagnose diabetes, and Hippocrates, the father of western medicine, wrote of the musty breath odor associated with liver disease. Smell has continued to be used widely in some countries - it is still taught in Mexican medical schools, for instance - but it has largely fallen out of favor in the U.S.
The smell of cancer presents a more difficult problem. Humans can't detect it. Neither can the most sophisticated machines. Now, Broffman's work with dogs suggests that breath diagnosis of cancer may be at hand, using low-tech dogs.
The dogs may remain the best hope for early detection for diseases such as lung cancer, which is without symptoms in the early stages when it is most treatable. The dogs would provide a quick and inexpensive test for the most likely victims of this cancer - current and former smokers.
As a high school student, Broffman knew little about cancer or China, and not a thing about traditional Chinese medicine. He loved to study, liked to box, and spent his spare time making money by rebuilding carburetors, which regulate gas flow to the engine in older model cars. When it came time to choose a college, he gave no thought to whether Asian studies was part of the curriculum; he simply wanted a school small and quiet enough that there would be few distractions from his studies. He chose Bowdoin. He arrived in the fall of 1971, hauling a bunch of carburetors that he planned to rebuild in his dorm room. The automotive repair business - with its attendant greasy smells - didn't sit well with his freshman roommate.
After one semester, Broffman had all the isolation he wanted; the College allowed him to move off campus where he could study, fix carburetors, and pursue his passion for vegetarian recipes. Most of these recipes turned out to be Chinese. And from that, Broffman developed a curiosity about China, its language, and the country's traditional medicine.
Bowdoin had little to offer on China at the time. Back then, American college curriculums tended to focus on our principal Cold War adversary, the Soviet Union. That didn't change until President Richard Nixon's 1972 trip to Beijing, which opened Sino- American relations.
But Bowdoin proved adaptable. When Broffman asked to study the Chinese language, the College allowed him to study for credit with the only Chinese speaker on campus, Rosie Huang, a college bookkeeper. This prepared him for an intensive Chinese language program at Cornell University, where he spent his junior year.
When Bowdoin's course offerings on Asian culture, politics, government, and religion also proved too litle to satisy Broffman's curiosity, the College allowed him to design his own major in East Asian Studies. After graduate study in Chinese medicine in Hong Kong and Taiwan, he opened his practice in affluent Marin County, just north of San Francisco. Had he opened the office in his native New York, he might have waited indefinitely for patients. In counter-culture California where his wife Annapurna, the clinic's co-founder had grown up, his practice was full within a week. At the time, he was one of three Chinese medicine specialists in Marin County. Today, there are 150.
One of the basic tenets of Chinese medicine is to pay attention to the world around you. Most anything could lead to new research breakthroughs.
Over the years, Broffman picked up on bits of anecdotal evidence that dogs seemed to react differently around their owners shortly before they were diagnosed with cancer. Broffman began to wonder if dogs had been reacting to some extremely subtle change in the breath. A Miami dermatologist picked up on similar bits of information and decided to see if dogs could be taught to recognize the smell of melanoma skin cancers. His tests, conducted several years ago, found that they could. But those findings offered no help for early detection of internal cancers, so Broffman's research team set up their own four-month trials which focused on breath samples. The trials were completed in August. The dogs work with cancers ranging from stage I, the earliest phase detectable by machines, to stage IV, where the cancer is quite advanced. Researchers would like to train the dogs to react to cancers that fall outside technology's radar screen, but this could prove difficult since they have no way to identify undiagnosed cancer victims.
But the four-month trials provided a sliver of hope that the dogs may already be able to detect cancers that fall below the threshold of machine detection. During the trials, the dogs would sometimes hesitate at a particular sample, look confused, and then move on. Those samples came from supposedly healthy donors. It was possible that the dogs were reacting to very early stage cancer, and then deciding the sample fell below the threshold that their trainer wanted them to identify. "The dog isn't trying to detect cancer, but to get a reward," said Tadeus Jezierski, the project's animal behavior specialist. "The dogs may have concluded that they were only supposed to identify the stronger scents." For that reason, the Pine Street Clinic research team plans to follow the health of these donors to see if they later develop cancer. Said Broffman, "If the donors of these samples get cancer in five years, it may mean that the dogs' hesitation meant they detected early signs of cancer."
Ultimately, Broffman hopes the dogs will be replaced by sensitive high-tech machine noses. Work on such devices is underway in Italy and New Zealand. For the moment, though, the dogs are better than any manmade device, just as they are better than any machine at sniffing out drugs and some types of explosives. And they could hold that edge for years to come. "It may be," said Broffman, "that the technology will not exist for 50 years that can do what the dogs can do."