"The nose always knows"

For years, dog owners have been informing their doctors about the apparent disease-detecting ability of their pets, and today those claims gain some credibility with the release of the first ever peer-reviewed scientific study showing that dogs can smell cancer. In the study, three cocker spaniels, one papillon, one Labrador, and one mongrel were trained for seven months to discriminate between urine from patients with bladder cancer and urine from healthy and otherwise-diseased patients. Whenever the dogs smelled cancer, they were taught to lie down in front of the sample. Each dog underwent nine trials, which consisted of six control samples and one positive urine sample. Some of the samples contained dried urine. The chances of a dog sniffing out a diseased sample were predicted to be correct 1 out of 7 times (14%), but actual research statistics showed they were correct 22 out of 54 times (or 41%). That's amazing. Dogs are more useful to their owners than we thought. One of the leaders advises dog owners to "pay attention if their pets exhibit unusual sniffing behavior related to a possible health issue, such as a skin mole." So three cheers for man's best friend!

Most of this information comes directly from http://dsc.discovery.com/news/briefs/20040920/dogcancer.html.