Anecdotal evidence that the ultra-sensitive noses of dogs can detect subtle olfactory signs of cancer abound, such as the story of a dog that kept sniffing a spot on a man's arm until he went to have it checked out -- only to find it was malignant melanoma. It turns out that these anecdotes reflect more than coincidence: researchers in San Francisco and Poland have run extensive tests showing that dogs can detect cancer by scent alone, even by smelling the breath of patients.
In this study, five household dogs were trained within a short 3-week period to detect lung or breast cancer by sniffing the breath of cancer participants. The trial itself was comprised of [sic] 86 cancer patients (55 with lung cancer and 31 with breast cancer) and a control sample of 83 healthy patients. [...] The results of the study showed that dogs can detect breast and lung cancer with sensitivity and specificity between 88% and 97%. [...] Moreover, the study also confirmed that the trained dogs could even detect the early stages of lung cancer, as well as early breast cancer.
The implications here are multifold: the potential for an extremely inexpensive, highly-accurate, non-invasive test for cancer; stimulus for tests of canine ability to smell subtle clues of other diseases; and an indication that there are detectable levels of molecular signs of early stages of cancer, with the possibility of engineering sensors that could be even more accurate and sensitive than dog noses.
