Study: Dog's Sensitive Schnoz Sniffs Out Prostate Cancer

(June 2) -- French researchers have tapped man's best friend to detect those at risk of developing prostate cancer, and it turns out that dogs might do a better job than a much-maligned blood test devised by modern medicine.

A team of researchers at Tenon Hospital in Paris trained a Belgian Malinois shepherd, already renowned for its ability to detect bombs, to sniff the urine of men already diagnosed with prostate cancer. The dog was able to correctly identify the urine of a prostate cancer patient, compared with the urine of four healthy individuals.

Bizarre as the idea sounds, it's already being tested for the identification of other cancers, including lung and breast cancers. Different kinds of tumors release specific chemical compounds whose odor can be picked up by ultra-sensitive noses -- like those of dogs.

For prostate cancer, those odors are apparent in urine. Lung and breast cancer, however, can be identified on a patient's breath.

Prostate-specific antigen, or PSA, blood tests administered to some 30 million American men each year are rife with false positives. Earlier this year, the American Cancer Society sparked debate among medical experts when it relaxed its preventative-testing guidelines in light of the inaccuracies.

The trained dog, however, misidentified only three healthy men as having prostate cancer, out of 66 samples. The dog also sniffed out every single prostate cancer patient in the trial group.

But even though canines are capable of impressive accuracy, the researchers, who presented their findings at this year's meeting of the American Urological Association, don't know exactly what the dogs are sniffing for.

"The dogs are certainly recognizing the odor of a molecule that is produced by cancer cells," lead researcher Jean-Nicolas Cornu told Business Week. "[But] we do not know what this molecule is, and the dog cannot tell us."

The benefits of earlier, more accurate diagnoses are obvious -- cancer that's caught early is easier to treat. But eliminating false positives would also have major implications by curbing the number of men treated unnecessarily.

A positive PSA test can result in surgery or radiation for men whose cancer would never have developed to become life-threatening. For every life saved by treatment, 47 men are treated needlessly, according to an analysis published last year in The New England Journal of Medicine. It took a year for the French team to train its cancer-sniffing canine, and the group is working with more dogs.

But the ideal result wouldn't be a dog in every hospital. Rather, researchers hope to figure out the chemical odors relevant to the diagnostic process and then develop an "electronic nose" that can do the dog's job.