In the small world of people who train dogs to sniff cancer, a little-known Northern California clinic has made a big claim: that it has trained five dogs - three Labradors and two Portuguese water dogs - to detect lung cancer in the breath of cancer sufferers with 99 percent accuracy.
It has been known since the 80's that tumors exude tiny amounts of alkanes and benzene derivatives not found in healthy tissue. Other researchers have shown that dogs, whose noses can pick up odors in the low parts-per-billion range, can be trained to detect skin cancers or react differently to dried urine from healthy people and those with bladder cancer, but never with such remarkable consistency.
The near-perfection in the clinic's study, as Dr. Donald Berry, the chairman of biostatistics at M. D. Anderson Cancer Center in Houston, put it, "is off the charts: there are no laboratory tests as good as this, not Pap tests, not diabetes tests, nothing.
As a result, he and other cancer experts say they are skeptical, but intrigued. Michael McCulloch, research director for the Pine Street Foundation in Marin County, Calif., and the lead researcher on the study, acknowledged that the results seemed too good to be true. (For breast cancer, with a smaller number of samples, the dogs were right about 88 percent of the time with almost no false positives, which compares favorably to mammograms.)
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