A labrador retriever called Marine has been trained to sniff out cancer with stunning accuracy, researchers report today.

The nine-year-old female successfully identified people with bowel cancer more than nine times out of 10 after being given samples of their breath or faeces to sniff. The discovery suggests that chemical compounds associated with specific cancers circulate in the body, opening up the prospect of developing tests for a range of cancers that could be applied even in the early stages of the disease.

However, researchers say it would be "impractical and expensive" to employ live animals and their trainers to screen patients, but a sensor might be developed to do the job instead. Marine was trained at the St Sugar Cancer Sniffing Dog Training Centre in Chiba, Japan. She began in 2003 as a water-rescue dog – trained to save people from drowning by dragging them to the shore – but in 2005 was switched to cancer detection. Over four years she learnt to distinguish the smell of a dozen different cancers including breast, stomach, prostate, bladder and skin cancer.

In the latest study of bowel cancer, Marine completed 74 sniff tests, each involving five samples of breath or faeces, only one of which was cancerous. To identify a sample she was required to sit in front of it and to ignore the other four samples after sniffing them. Each time she correctly identified the cancerous sample she was given a reward.

The samples came from 48 people with confirmed bowel cancer and 258 disease-free controls. Marine got the right answer in 33 out of 36 breath tests and 37 out of 38 faeces tests – a 95 per cent accuracy rating.

Hideto Sonoda, of Kyushu University, who led the study published in the journal Gut, said: "She presumably reacted to a smell unique to cancers. If we can identify the material causing the smell, it may lead to early cancer detection."

Existing methods of bowel cancer detection rely on testing faeces for signs of internal bleeding that are invisible to the eye, but the test detects early stage disease in only one in 10 cases.

Bowel cancer is the second-biggest cancer killer in the UK after lung cancer, claiming 16,000 lives a year. It is 90 per cent curable if detected early.