And maybe someday a machine can do what the dogs do. Manssana Research is developing a breathalyzer that could detect organ rejection, diabetes, tuberculosis as well as cancer.
"I think it's a complicated bunch of smells," said Harvey Pass, head of thoracic surgery at NYU Medical Center. Pass has been involved in trials of the breathalyzers.
"We want to find something early. We want to do it though without harming patients, and we want to be accurate in its assessment, and I think that breathalyzers are going to be improved," Pass said.
Even though she's no longer skeptical that dogs can smell cancer, Willis says she's never imagined them in clinics performing any sort of diagnosis.
Pass isn't so sure…
"Could you imagine you have the early detection clinic that's in a given area of the hospital, that people would come, and then they'd go into a room and there's a series of dogs, that then look at them and they either lie down, or they sit up, and just that signal may tell you what's going on. I wouldn't bet against it," he said.