This is amazing! More research is on the way, but still… WOW! I wonder how much it would cost to train dogs to sniff out cancer and if it would be worth it as a screening pre-screen for people with no symptoms but of an age to start being checked.
COSMOS Magazine, Paris: Japanese scientists have found that dogs can distinguish people with colorectal cancer, reporting that a retriever can scent bowel cancer in breath and stool samples as accurately as hi-tech diagnostic tools.
The findings published in the British Medical Journal support hopes for an ‘electronic nose’ that will one day be able to sniff out the specific chemicals that are produced by cancer cells and circulate in the blood stream before being expelled by the lungs.
Researchers led by Hideto Sonoda at Kyushu University in Fukuoka, Japan, used the specially-trained female black labrador to carry out 74 ‘sniff tests’ over a period of several months. Each of the tests comprised five breath or stool samples, only one of which was cancerous.
95% on breath tests
The samples came from 48 people with confirmed bowel cancer at various stages of the disease and 258 volunteers with no bowel cancer or who had had cancer in the past. They complicated the task for the eight-year-old canine detective by adding a few challenges to the samples.
Around half of the non-cancer samples came from people with bowel polyps, which are benign but are also a possible precursor of bowel cancer. Six percent of the breath samples, and 10% of the stool samples, came from people with other gut problems, such as inflammatory bowel disease, ulcers, diverticulitis, and appendicitis.
The retriever performed as well as a colonoscopy, a technique in which a fibre-optic tube with a camera on the end is inserted into the rectum to look for suspect areas of the intestine. It correctly spotted which samples were cancerous and which were not in 33 out of 36 breath tests, equal to 95% accuracy, and in 37 out of 38 stool tests (98% accuracy).
Hopes for early cancer detection
It performed especially well among people with early stage disease, and its skills were not disrupted by samples from people with other types of gut problems. Previous research has also found that dogs can sniff out bladder, lung, ovarian and breast cancer.
Using dogs as a screening tool is likely to be expensive. But the success of this experiment backs hopes for developing a sensor that can detect specific compounds, in faecal material or the air, that are linked to cancer.
There is already a non-invasive method for screening for bowel cancer, which looks for telltale traces of blood in a stool sample. But it is only about 10% accurate in detecting early-stage disease.
Further tests on more cancers required
“There have been rumours floating around about dogs being able to “smell cancer’ on the breath of people with bowel cancer and it’s good to see some solid research to back it up,” said gastroenterologist Graeme Young, a specialist in colorectal cancer at Flinders University, South Australia.
“Dogs have an incredibly acute sense of smell and can be trained to detect these chemicals in the breath of cancer patients with a remarkable degree of accuracy.”
“An important question is whether these molecules are specific to colorectal cancer or whether they are also given off by other cancers. It may be, for example, that different groups of cancer with different genetic make-ups give off different chemicals. So a range of tests will need to be done on a variety of cancers to confirm the reliability of this type of screening technique,” said Young.
The dog used in the Japanese experiment was initially trained for water rescue in 2003 and then began training as a cancer detector in 2005. Every time she correctly distinguished a cancer sample, she was allowed to play with a tennis ball.