How do dogs sniff out cancer?

Darren - So, dogs have incredibly well-developed sense of smell. In fact, dogs and rats we think are perhaps the best smellers in the animal kingdom. And so, a number of groups recently have been using this sort of very sensitive nose that dogs have to see if we can use them to detect chemical patterns that are associated with certain diseases. It's been done prostate cancers and also ovarian cancers with women. It does appear dogs can detect differences in smells in urine after people have cancer. Quite what the chemical is the dogs are sensing we don't know, so we can't set up a diagnostic screening yet with these chemicals.