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January 17, 2006

This doesn't pass the smell test

If dogs can sniff out cocaine, then surely they can sniff out lung cancer, right? They can, according to researchers quoted in a New York Times article today ("Dogs Excel on Smell Test to Find Cancer").

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.

The study was based on well-established concepts. It has been known since the 80's that tumors exude tiny amounts of alkanes and benzene derivatives not found in healthy tissue.
Needless to say, there are skeptics.
Experts who read the study raised various objections: The smells of chemotherapy or smoking would be clues, they said. Or the healthy breath samples could have been collected in a different room on different days. Or the dogs could pick up subtle cues - like the tiny, unintentional movements of observers picked up by Clever Hans, the 19th-century "counting horse," as he neared a correct answer. But Mr. McCulloch said cancer patients who had begun chemotherapy were excluded, smokers were included in both groups and the breath samples were collected in the same rooms on the same days. The tubes were numbered elsewhere, he said, and the only assistant who knew which samples were cancerous was out of the room while the dogs were working.
But the point I want to raise isn't raised until the last paragraph of the article. (Apparently, the Times, like the Washington Post, uses the "double-inverted pyramid" style of newspaper writing.) That point is this: So what?
Even if the dogs are accurate in repeat experiments, Dr. Gansler of the American Cancer Society said, it will be useful only as a preliminary scan. "It's not like someone would start chemotherapy based on a dog test," he said. "They'd still get a biopsy."
So this whole thing is basically a party game. Tell me why I'm wrong.