Sniffer dogs can be used to reliably detect lung cancer, according to researchers in Germany.
Writing in the European Respiratory Journal, they found that trained dogs could detect a tumour in 71% of patients.
However, scientists do not know which chemical the dogs are detecting, which is what they say they need to know to develop a screening program.
It was first suggested that dogs could “sniff out” cancer in 1989 and further studies have shown that dogs can detect some cancers such as those of the skin, bladder, bowel and breast.
It's Interesting 
very interesting…i must say i am not surprised…i mean there are dogs that detect an impending seizure in an epileptic person…amazing..