Cancer diagnosis and cancer screening for colorectal cancer
A sigmoidoscope is a narrow tube with a light at the end. Inserted in the rectum it can find polyps and tumours in the lower colon. By contrast a colonoscopy is a longer tube and looks further in to the colon.
Sigmoidoscopy reduces bowel cancer rates - Despite Government promises about two years ago to bring in colorectal screening annually for the over 50’s nothing much has happened to date. Now new research should cause some action.
A five minute ’flexi-scope’ examination called sigmoidoscopy has been found in Clinical Trials to reduce the risk of developing colorectal cancer by a third and deaths from the disease by 43 per cent.
The prevention technique looks for inflammation and the formation of polyps which can lead to a cancer. These can easily be removed if caught early.
The research involved 170,000 men over 11 years and was published in the Lancet.
The figures suggest that this test if performed annually, might prevent around 10,000 cases per year and 6,000 lives. Recent Canadian research on these tests and covered in Cancer Watch suggested however that they missed certain areas of the colon.
Currently testing focuses on the over 60’s and involves a stool test looking for signs of bllod every two years. Cancer Research has dubbed sigmoidoscopy, a ’Breakthrough’.
The UK Health Minister announced at a national cancer conference a few years ago that he is intending to introduce a national bowel cancer screening programme for everybody over the age of 50 but we are still waiting. Expense seems the issue, although people who have a family history of colorectal cancer can ask for an annual check and in America such people have a check automatically every two years searching for pre-cancerous polyps.
However, 2008 research from the University of Toronto concluded that colonoscopy missed just about every cancer starting in the right side of the colon, and about one third of those starting on the left side. So shocked were the researchers that they re-ran the tests, but still got the same results.
Another approach is the less accurate blood stool test which tests faeces for early signs of cancer.
How accurate are colonoscopies really?
A Canadian report from the University of Toronto and published in the Annals of Internal Medicine in December 2008, is causing serious concerns, after it concluded that colonoscopies missed just about every cancer starting in the right side of the colon and about one third of cancers starting in the left side. ’This is a really dramatic result. It makes you step back and worry; what do we really know?’ said David Ransohoff, a gastroenterologist at the University of North Carolina, and reported in The New York Times. The lead Toronto researcher, Nancy Baxter, described the results as ’a shock’ and even asked the team to rerun the tests!
This study follows a previous one in Spring 2008 where colonoscopies were found to miss a flat lesion or inverted polyp that develops against the colon wall.
The theory goes that people over 50 can have a colonoscopy every two years to spot pre-cancerous polyps. Remove these and the threat of a cancer diminishes greatly.
’We have to not overpromise’, added Ransohoff who wrote the accompanying editorial to the paper. ’Colonoscopy is a good test, but it isn’t completely protective’.
A less accurate, but less onerous blood stool test is another possibility.