19 April 2009

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.

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—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.

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. So, the question is, Does cancer have a smell?

Cancer Have a Smell?
Is there something about the breath of people with cancer that is different in people who do not have cancer?

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. The African pouced 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.

The link between a dog’s smell and its ability to detect hypoglycemia is well established. When blood sugar starts to drop, the body starts to kick out chemicals in the breath, sweat. 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, a 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 can pick up on other smells that humans can’t when glucose levels drop.

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.

Toward The Future
Scientists may be years from identifying the specific biomarkers that distinguish the breath of people with cancer from those without.

It would be great to have a Breathalyzer-type machine that could do this. The goal is to identify what collection of molecules are unique to ovarian cancer, pancreatic cancer, or lung cancer, and can it be developed a test to find those. That’s because this wouldn’t require just detecting one molecule but a range of molecules. 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, yes that’s rose.

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. No scent detection device on the planet that 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.


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