Population screening for bowel cancer

Colorectal cancer is the second most common cause of cancer death in both sexes, killing around 1600 people in Scotland every year. Research led by Professor Bob Steele has resulted in changes to the UK’s colorectal cancer screening programme, saving around 2000 deaths per year and providing a model for similar programmes in other countries.

Population screening is used to detect early signs of disease in people who appear healthy, but who might be at an increased risk of developing a particular disease or condition. Screening allows diagnosis, referral and treatment and is currently the most effective way to detect colorectal cancer at a stage when it can be treated successfully.

Earlier work conducted by Steele and his team (described in a REF2014 case study) had established that the faecal occult blood test was an effective way to screen for colorectal cancer. The test proved sufficiently accurate and sensitive to detect early indicators of the cancer, allowing treatment before disease could progress further, and the approach subsequently led to the introduction of UK-wide screening programmes for colorectal cancer.

In the intervening years, the Dundee team has continued to work on the screening programme under the directorship of Steele. The faecal occult blood test used on the original screening programmes is an indirect measure of human haemoglobin in faeces, whereas the faecal immunochemical test (FIT) specifically detects haemoglobin. The Dundee team established that FIT could be used to follow up weakly positive occult blood tests, reducing the number of false positive results. Further work established the superiority of quantitative FIT over the original faecal occult blood test, detecting 20% more cancers and 40% more adenomas in routine use.

FIT has also been shown to be a safe and effective ‘rule out’ test, showing that the absence of detectable haemoglobin in faeces is associated with a very low risk of disease. This assists decision making for the investigation of symptomatic patients, reducing the number of referrals for invasive colonoscopy, without any negative impact on rates of diagnosis of serious disease – thus saving time and money for the NHS and reducing the need for face-to-face appointments during the COVID-19 pandemic.

Further, similar, benefits have been realised through randomised control trials, which provided evidence to justify discontinuing the use of flexible sigmoidoscopy as a screening method for colorectal neoplasia. As a result, the decision was made not to adopt flexible sigmoidoscopy as a screening method in Scotland, and in July 2020 the UK National Screening Council agreed to discontinue its use in England.  

Following implementation of the Scottish Bowel Screening Service in 2007, mortality from colorectal cancer in Scotland has fallen by 8%, and by October 2018 an estimated 6000 colorectal cancers had been diagnosed through screening.

Image credit: Public Health Scotland

Read more about research impact from the School of Medicine

Read the 2014 REF case study

Annie Anderson and Bob Steele discuss bowel cancer research at the University of Dundee