London: They are called the man`s best friend, but dogs are more than just a faithful companion as they can be trained to detect lung cancer much before symptoms develop, scientists say.
Researchers from Schillerhoehe Hospital in Germany found that dogs, known for their ability to detect smells that escape the human nose, can identify a tumour in 71 percent of patients if trained properly.
They believe dogs could become even better at picking up cancer cases with more practice, the Daily Mail reported.
But the ultimate goal is to identify the cancer-specific chemical compounds the dogs can smell and develop a device that could be used to help diagnose lung cancer victims at an earlier stage, they said.
For their study, published in the European Respiratory Journal, the researchers trained four dogs -- two German shepherds, an Australian shepherd and a Labrador -- to detect in the breath of patients a volatile organic compound (VOC) which is linked to the presence of cancer.
The team worked with 220 volunteers, including patients with lung cancer at early and advanced stages, patients with chronic obstructive pulmonary disease and healthy volunteers.
The dogs took part in a number of tests to see if they could reliably distinguish compounds in the breath of lung cancer patients -- even if they smoked.
It`s found that the dogs correctly identified 71 samples with lung cancer out of a possible 100. They also detected 372 samples that did not have lung cancer out of a possible 400.
Dr Thorsten Walles, who led the research, 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."
The dogs could also detect lung cancer independently from COPD, prescription drugs and tobacco smoke, the researchers said.
The findings confirm the presence of a stable marker for lung cancer -- but the snag is they do not know what it is, they said.
Co-researcher Enole Boedeker said that the dogs were very excited by the "game" and were rewarded by treats when they got it right.
She said: "The trainer would shout `Cancer -- go` and off they went, sometimes identifying a VOC straight away and at other times they hesitated and then went back.
"They had around 11 weeks of training but seemed to get better the more they did, I think the success rate could go higher.
"However, they have been trained in a certain way using samples so even if they did go into a room with someone who had lung cancer it might be difficult for them to register it, which is why we need to investigate a screening tool," she added.
Previous research has suggested dogs -- usually Labrador retrievers and Portuguese water dogs -- can sniff out bladder, skin, lung, breast and ovarian cancers.