Tests found that trained animals correctly identified 71 per cent of people who had the disease and correctly dismissed 93 per cent of those who were healthy.
They were able to distinguish between people who had tumours and those who had chronic obstructive pulmonary disease, a separate condition also linked to smoking, according to a paper published in the European Respiratory Journal.
Scientists at Schillerhoehe Hospital in Germany believe that dogs, long used by police to sniff out drugs, are able to use their sensitive noses to detect chemicals known as volatile organic compounds that are present in cancer sufferers and exhaled in their breath.
The study author, Thorsten Walles, said: “In the breath of patients with lung cancer, there are likely to be different chemicals to normal breath samples and the dogs’ keen sense of smell can detect this difference at an early stage of the disease. Our results confirm the presence of a stable marker for lung cancer.
“This is a big step forward in the diagnosis of lung cancer, but we still need to precisely identify the compounds observed in the exhaled breath of patients. It is unfortunate that dogs cannot communicate the biochemistry of the scent of cancer!”