Study alters perception of colonoscopy efficacy

In collaboration with the Press Association

A Canadian study has confirmed the effectiveness of colonoscopy as a means of preventing cancer deaths, it has been revealed. Colonoscopy is a technique that allows doctors to see inside the bowel, so pre-cancerous growths or tumours can be spotted and removed.

However, the research, which appears on the Annals of Internal Medicine website, also shows that the test has its limitations.

Scientists assessed the health records of people aged between 52 and 90 who had died of bowel cancer by 2003 having been diagnosed with the condition between 1996 and 2001.


A control group was also created which was made up of people from Ontario, Canada, who had not succumbed to the disease.

While a colonoscopy was found to help reduce the number of deaths associated with cancer on the left side of the bowel, it was found to be ineffective in the fight against right-sided bowel cancer.

"Although improvements in the quality of screening colonoscopy may improve detection at the right side, differences in tumour biology may limit the potential to prevent right-sided colorectal cancer deaths with current endoscopic technology," commented Dr Nancy Baxter, a researcher at St Michael's Hospital and the study's lead author.

"Nevertheless, this study clearly demonstrates that colonoscopy is an effective procedure for the prevention of death from colorectal cancer, it just may not be quite as effective as we've thought in the past."

In light of the new data, Dr David F Ransohoff, the author of an editorial which goes hand in hand with the study, believes doctors should no longer advise patients that a colonoscopy can reduce the risk of dying from bowel cancer by 90 per cent.

Rather, he suggests a figure of between 60 and 70 per cent should be quoted.

Professor Wendy Atkin, a Cancer Research UK bowel cancer expert, based at Imperial College London, said:

"This intriguing study confirms that looking in the rectum and lower part of the bowel - or left side - is the most effective way of reducing deaths from bowel cancer. Cancer Research UK and the Medical Research Council are funding a large trial to examine the effectiveness of a test called flexible sigmoidoscopy, which examines the left side of the bowel, across the whole population as a one off test.

"It's not clear from this Canadian study why colonoscopy isn't as effective at picking up cancer in the right side of the bowel. It may be because of the performance of the examination, or because growths develop in a much different way in this side of the bowel. Cancer Research UK is funding a large study called PROXY which aims to find out what can be done to detect and prevent more cancers in the right side of the bowel.

"In the UK, routine colonoscopy screening is not recommended as a method of preventing bowel cancer, unless people have a strong family history of the disease. Thanks to a recent Department of Health initiative, the quality of colonoscopy screening is now at a very high standard in the UK. In addition to a colonoscopy, there are a number of tests that doctors use to detect bowel cancer, which include sigmoidoscopy, CT scans and x-rays.

"The National Bowel Screening Programme in the UK offers a test to detect bowel cancer in men and women between the ages of 60 and 69. This test looks for hidden blood in the stool. Around two per cent of people who have this test will have an abnormal result and will be invited to have a colonoscopy ? and many early cancers and pre cancerous polyps have been detected in this way. We encourage people who are offered this test to take up the opportunity ? catching cancer before symptoms become obvious means treatment can start promptly and more patients can be cured."

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