A small study recently suggested that dogs may be able to learn to determine which men have prostate cancer - simply by smelling samples of human urine.
The study, from doctors at the University of New Mexico and recently presented at the American Urological Association meeting in San Francisco, seemed to show that a trained dog could choose the select the sample of a prostate cancer patient out of a group of normal samples nearly every time (63 out of 66 times according to the authors).
While researchers have been paying more attention to the disease-detecting abilities of animals in recent years, this type of research is currently still fraught with sources of potential error (or misinterpretation). For example, many researchers believe that animals simply pick up on subconscious cues from nearby humans who know which patient is sick or which sample is contaminated.
Additionally, while more and more studies are being done that seem to show an ability of animal's to detect various diseases or contaminants, this doesn't readily translate into a benefit for human beings.
In the case of the urine-sniffing dog above, if the dog is detecting a particular compound in the urine of the prostate cancer patients, this does not necessarily help in determining what that compound is nor how it can be measured.
Overall, these animal studies are interesting, but likely are still many years from translating into something directly useful for prostate cancer patients.