The Screening Gap
What is screening?
Screening is the process of identifying disease in people who have no symptoms with a
view to detecting a disease early so that it can be treated effectively or even prevented. In the UK we have national screening programmes in each nation in which individuals aged 60-74 in England, Northern Ireland and Wales and from age 50 in Scotland. These individuals are sent a home testing kit, known as the faecal occult blood test (FOBt), every two years. In England another screening test, Bowel Scope, in which individuals aged 55 are offered a one-off flexible sigmoidoscopy is being rolled out.
What is the evidence?
We know that nine out of 10 people will survive bowel cancer if detected in the earliest stages of the disease and we also know that removing polyps, which can develop into cancerous tumours, prevents it. Robust evidence shows that testing for small amounts of blood in stools is effective in detecting bowel cancer early, helping to reduce deaths from the disease by 16 per cent if a 60 per cent uptake is achieved. A new screening test, Faecal Immunochemical Test (FIT), is being piloted as a replacement for the FOBt. This test can be more sensitive test than the FOBt and therefore could be more likely to detect more cancers or pre-cancerous polyps. It also only requires one stool sample rather than three, which makes the test much more acceptable to people. There is also evidence to show that screening with an endoscope to look at the left side of the colon (flexible sigmoidoscopy) could save 3,000 lives a year.
What are the gaps in screening research?
The evidence in favour of national bowel screening programmes is strong. However, if we want to broaden our understanding of screening and improve the effectiveness of the programme there are still many more questions that need to be answered, which could help to save more lives. Here are just some areas where more research is needed:
- FIT for purpose: The new screening test, FIT, is more accurate than the current FOBt, can improve uptake and the sensitivity of the test can be adjusted. However we don’t know what the most appropriate concentration of blood is to trigger a colonoscopy, how often testing for blood in stools should take place and whether the concentration of blood should vary according to age and gender, given bowel cancer is more prevalent in some populations than others. For example, men are more likely to develop bowel cancer than women and risk increases with age.
- Endoscopic screening: The roll out of Bowel Scope Screening is well underway in England and Scotland is looking at the feasibility of introducing this as a one-off test at age 55. As Scotland already screens from 50 using the FOBt and is in the process of replacing this with the more accurate FIT, should flexible sigmoidoscopy screening be introduced and would it be useful in such a population? A further question to answer is whether a colonoscopy would be an appropriate screening test, and if so, how often and at what age should it be offered?
- Increasing participation: The level of uptake for screening is still very low with no nation in the UK meeting the 60 per cent target. We need to know how we can improve uptake rates for all types of screening; whether that is through targeted and tailored interventions on the benefits of screening aimed at low-uptake groups to meet their specific needs or the involvement of primary care. A one-size fits all approach cannot be taken. There is also the possibility of linking bowel screening with other types of screening which have higher uptake rates, for example breast screening.
- Freeing up endoscopy resources: The demand for endoscopy is due to increase dramatically over the next five-year owing to increased awareness of symptoms. It will therefore be very important to find out if screening tests be used to identify which symptomatic patients should be referred for colonoscopy. This could free up colonoscopy resource for screening itself.
- Screening and prevention: There is now evidence that linking screening with the delivery of health messages to advocate lifestyle change are effective, and we need to build on this to raise the profile of primary prevention of bowel cancer.
We have achieved much in bowel screening but it is clear that there is still much more to do!
By Bob Steele, Professor of Surgery and Head of Cancer Research, University of Dundee