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Dogs Sniff Out Clues in the Fight Against Cancer
By Sean Kelley
They've got funny names for cancer researchers, like Captain Jennings and Tibbs. They're also a little furry and have a tendency to lick their white-coated colleagues. But these canine lab assistants may one day make it possible to detect cancers early enough to keep them from becoming fatal.
The Pine Street Foundation, a cancer education and research center in San Anselmo, Calif., is hoping one day to train these dogs to sniff out, literally, early-stage ovarian cancer. It's a disease that kills two-thirds of the 22,000 women diagnosed with it each year, according to the American Cancer Society, because it is often caught only after it has spread beyond the ovaries.
In 2006 the foundation published a study showing it was possible to train dogs to identify, based on breath samples, which patients had lung and breast cancer. Now the organization is recruiting ovarian cancer patients and dogs for a new study.
Nicholas Broffman, executive director of the foundation, says the dogs are helping to answer an important question that may one day lead to earlier detection of diseases like ovarian and pancreatic cancers, which are often caught only in very late stages: Does cancer have a smell?
Does cancer have a smell?
"Is there something about the breath of people with cancer that is different in people who do not have cancer?" Broffman wants to know. "Our goal is to identify what collection of molecules in the breath are unique to ovarian cancer, pancreatic cancer, and lung cancer, and develop a test to find those." Using animals to detect disease is not new, and this line of research is not as out there as it may sound. The African pouched rat has been trained to detect tuberculosis in Petri dishes. By some accounts, they are better and more efficient at spotting the disease in tissue samples than other conventional methods in the developing world.
Diabetes is detectable, too
Dogs, which have been used for decades as aides for the blind or hearing impaired and as companions for the infirm, have also taken new roles in alerting epileptics to impending seizures and diabetics to low blood sugar.
A few dozen miles east of the Pine Street Foundation, in Concord, Calif., Mark Ruefenacht, who runs Dogs4Diabetics, says the link between a dog's smell and its ability to detect hypoglycemia is well-established. He’s been training dogs for 10 years to pick up the scent of diabetics on the verge of hypoglycemia.
"We don’t know the complete science here, but when blood sugar starts to drop, the body starts to kick out chemicals in the breath, sweat, whatever," Ruefenacht says. "Those chemicals indicate a change. The dogs can pick that up. Low blood sugar has a smell; high blood sugar has a smell; even the rapid change in blood sugar has a smell."
In diabetics, the presence of ketones—substances produced by the body as it breaks down fat for energy—can be smelled in urine and on the breath when blood sugars are high. Dogs, Ruefenacht says, can pick up on other smells that humans can't when glucose levels drop.
These chemical scents are what scientists at the Pine Street Foundation and the University of Maine, which is helping in the ovarian cancer study, hope to identify for ovarian cancer. The research is still in its infancy, but researchers are clearly excited about the potential—and they're not alone.
In a case study published in The Irish Journal of Medical Sciences last year, researchers claimed that a family pet had recognized hypoglycemia in an elderly man who had never been diagnosed with diabetes.
"Dogs have a sense of smell far superior to humans," says study coauthor Mortimer O'Connor, M.D., of Victory University Hospital in Cork, Ireland. Smell is just one way dogs may detect a condition change like low blood sugar, O'Connor says; he also suggests that they may taste a difference on a person’s skin or sense changes in the electric or magnetic energy the body emits.
Looking toward the future
Scientists may be years from identifying the specific biomarkers that distinguish the breath of people with cancer from those without, cautions Broffman—and years more from being able to distinguish one type of cancer, such as ovarian, from another.
Even further in the future: Developing a mechanical device that can sense those biomarkers when someone breathes into it. "It would be great to have a Breathalyzer-type machine that could do this," Broffman says."Our goal is to identify what collection of molecules are unique to ovarian cancer, pancreatic cancer, or lung cancer, and can we develop a test to find those. Scientifically, this is very difficult."
That's because this wouldn't require just detecting one molecule—which is difficult enough—but a range of molecules, Broffman says. "Together, these molecules smell like cancer. When we smell a rose, we're not smelling individual rose molecules, but our brain puts all the molecules together and says, 'OK, that's a rose.'"
For a computer to accomplish that level of pattern recognition, Broffman says, the patterns have to be extremely well-defined. "This is the challenge, scientifically. This may be why we never replace dogs. Maybe dogs will be always be better at this."
Dogs can detect scents as small as one part per trillion—or the equivalent of a drop of ink in an Olympic-sized swimming pool, Broffman says. "No scent detection device on the planet can come close to that."
So for early detection of such diseases, scientists' best bet for now has four legs and a tail—and may one day be known as the cancer patient's best friend.