New bowel screening kits, expected soon for England and Scotland, are more sensitive at picking up pre-cancerous growths in the left-side of the bowel than the right-side because the growths are shaped differently.
The research* conducted in Germany and published in the British Journal of Cancer** today (Wednesday), helps shed light on the characteristics of pre-cancerous growths in the right-side of the bowel which may explain why screening is less sensitive in that area.
These insights could help improve screening for bowel cancers in the future.
In Germany men and women over the age of 55 are offered screening for bowel cancer with colonoscopy.
The study invited around 2300 people awaiting routine colonoscopy screening for an immunochemical Faecal Occult Blood test (iFOBt) – a test for hidden traces of blood in the stools, which can be a sign of cancer or pre-cancerous growths in the bowel.
Comparing the results of colonoscopy to the iFOBt revealed how good the screening kit was at picking up pre-cancerous growths in the bowel.
The results showed that the iFOBt is less sensitive at detecting potentially cancerous growths in the right-side of the bowel – a finding supported by previous studies.
This study suggests that it may be because pre-cancerous growths in this part of the bowel are a different shape to those in other parts. Around 40 per cent of tumours are found in this right-hand side of the bowel.
Scientists found that the pre-cancerous growths – known as adenomas – in the left-side of the bowel are more likely to be stalk-shaped. The growths on the right-side had a flatter shape.
The stalk-shaped polyps may be more likely than others to bleed in small amounts – which can be detected by iFOBt.
Dr Ulrike Haug, lead study author based at the German Cancer Research Centre in Heidelberg, said: “Our study provides important information to estimate the effectiveness of FOBT-based screening programs for preventing right- versus left-sided colorectal cancer.”
At present the bowel screening programme in the UK uses gFOBt (guaiac FOBt) test which like the iFOBT detects hidden traces of blood in the stools. This test is available to men and women aged 60-74 in England, Wales and Northern Ireland and those aged 50-74 in Scotland.
The Scottish and English bowel screening programmes are looking to change to the more effective, and easier to complete iFOBt test in the near future. And in 2012, the screening programme in England will also incorporate the new Flexi-Scope test.
Previous evidence suggests that the gFOBt can also miss adenomas in the right-side of the bowel.
Bowel cancer is the third most common cancer in the UK with about 40,000 people diagnosed with the disease each year – more than 100 people each day.
The bowel screening programme has only been fully up and running since 2010 but it is thought to save 2000 lives each year in the UK.
Sara Hiom, director of health information at Cancer Research UK, said: “This study gives a valuable insight into how the iFOBt test works and will help guide improvements to the bowel screening programme in the future.
“Cancer Research UK welcomes the move to iFOBt – even though it’s not flawless, it’s an improvement on the present system.
“FOBt has been effective in detecting bowel cancer and saving lives. The addition of the new Flexi-Scope test from next year will further improve screening, and crucially will also help prevent the disease developing in the first place by identifying and treating pre-cancerous growths in the bowel.
“We know that when bowel cancer is found at the earliest stage, there is an excellent chance of survival and more than 90 per cent of people survive the disease at least five years.
“So it’s really important to take up the opportunity to use the free bowel screening kit when it comes through your door. Also if you notice changes to your bowel habit like blood in your poo, looser, more frequent bowel movements lasting more than three weeks, don’t delay – go see your doctor.”
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**Haug, U et al., Sensitivity of immunochemical faecal occult blood testing for detecting left versus right-sided colorectal neoplasia, British Journal of Cancer (2011)
*Part-funded by the German Research Foundation (DFG)
The iFOBt is being trialled in Scotland as a replacement for the gFOBt. The Scottish government will await the results of this trial before making a decision on the introduction of the Flexi-Scope test.
The iFOBt is used in Scotland when the result from the gFOBt is unclear and retest is needed.
The UK government has committed to adding the Flexi-Scope test bowel screening test from next year in England. The new test uses a camera and light at the end of a flexible tube to detect and remove pre-cancerous growths from the lower parts of the bowel.
Cancer Research UK scientists led the trial which showed that the Flexi-Scope test has the potential to prevent a third of bowel cancer cases in people screened, as well as picking up the disease earlier.
Early detection is vital for improving survival for bowel cancer. If the tumour is advanced when it is diagnosed, fewer than one in 20 people survive for five years.