Sniffer dogs can be used for early detection of lung cancer, according to research published in the European Respiratory Journal.
The dogs found 71 out of a possible 100 lung cancer cases by sniffing samples of a patient's breath. They also could dependably rule out lung cancer in 93% of the cases they were tested on -- 372 out of 400.
Earlier studies showed that dogs could also detect prostate, breast, ovarian and bowel cancer. Current diagnostic tests often fail to detect cancer in the earliest stages and at the same time expose a patient to the harmful effects of radiation, as a reporter mentions in Science Daily, where the dogs story is reported.
I bet the dogs, no matter how good they can become at cancer detection, no matter how low-cost the detection program, will never be used commercially. You can't patent the dog's sniffing ability, so you probably can't find a way to make a billion from canine cancer consultants.
I'd love to be proved wrong.