17 August 2022

The NHS is still catching up on the many hundreds of thousands of patients who missed screening appointments largely because of fear of contracting Covid-19 in hospitals during lockdowns.

On top of the demand caused by the Covid-19 backlogs, parts of England are lowering the starting age for bowel cancer screening for people turning 50 rather than 60 years old. This is going to mean even more pressure on already stretched hospital services.

The need to clear backlogs and process rising numbers of individuals needing bowel investigations through colonoscopies (tiny cameras that look inside the colon for signs of cancer or other disease) is a major consideration in this new research paper led by QMUL.

Positively, this QMUL-led study offers evidence that suggests it would be possible to reduce demand for colonoscopies with only a small reduction in early detection of cancer by changing the thresholds of faecal blood tests that trigger an invitation for a colonoscopy.

Bowel cancer is the fourth most common cancer but sadly is the second highest cause of fatalities, leading to 37 deaths each day in England. Failure to pick up early signs of the disease when it is most easily and effectively treated results in sharply rising numbers of fatalities the later bowel cancer is diagnosed.

Bowel Research UK’s own research for our #auguts #HaveYouGotTheGuts campaigns highlights the importance of people not being embarrassed to see their GP with possible symptoms of bowel cancer.

In a new poll we found over a quarter (26%) had chosen to avoid discussing their bowels with a GP, while over four in ten (42%) said their reluctance to see a GP about bowel issues led to a delay in receiving a formal diagnosis of their condition. This resulted in more than half (55%) saying that delays negatively impacted their treatment options.

We are also supporting research around bowel disease screening, one research project we are funding looks at swapping the current home poo test kit for bowel cancer for a more acceptable blood test. Another project (involving our Patients and Researchers Together network) is investigating how artificial intelligence data analysis might improve cancer detection while surgeons are actually conducting colonoscopies.

Where are we right now?

In most parts of England, women and men aged 60 to 74 years are offered CRC screening two-yearly. People receive in the post a home testing kit – FIT, to detect the amount of blood in poo samples. If the amount of faecal blood hit levels that warrant investigation, they are referred to hospital where they usually receive a colonoscopy to look for further signs of bowel cancer.

Some parts of England are offering FIT for bowel cancer at a lower age, as low as 50 years old in some regions. But screening is currently restricted because demand for endoscopic services such as colonoscopy is greater than capacity, and the continued presence of Covid-19 (which demands hygiene protocols that minimise the risk of transmission) continues to slow the numbers of patients receiving hospital examinations.

Data analysis

This QMUL-led research analysed data from the English Faecal Immunochemical Testing pilot in 2014, comprising 27,238 individuals aged 59-75, who were screened for bowel cancer using FIT.

The study showed that current two-yearly screening with a faecal haemoglobin threshold of 120 μg/g would generate an estimated 16,092 colonoscopies, would detect 1142 colorectal cancers, and prevent 186 colorectal cancers and 191 deaths per 100,000 screened over 15-years.

Increasing the faecal haemoglobin threshold to 180 μg/g would reduce required colonoscopies to 11,500, detect 1077 colorectal cancers, and prevent 131 colorectal cancers and 151 deaths. Changing two-yearly screening to three-yearly would reduce required colonoscopies to 10,283, detect 909 colorectal cancers and prevent 126 colorectal cancers and 138 deaths. Increasing the faecal haemoglobin threshold was estimated to be more efficient than increasing the inter-screening interval regarding overall colonoscopies per screen-benefited cancer.


The frequency of screening and the positive threshold for referral, both have strong influence in terms of early detection, prevention, and reduction in deaths, but they also impact on the numbers of colonoscopies required, where there is currently fixed capacity.

According to QMUL’s results, if screening programmes were adjusted to accommodate colonoscopy availability, it would be more effective to alter thresholds for positive tests rather than change testing intervals (although both could be done at once).

If, for example, we needed to reduce the current numbers of colonoscopies by about one third, this could be achieved by either changing the interval from two to three years or changing the threshold from 120 µg/g to 180µg/g. However, QMUL estimate the lives lost due to the latter change would be considerably fewer – around 400 lives for every 3 million screened over 15 years.

Combined changes to both threshold and frequency can be very powerful. For example, we could increase the numbers of lives saved by around 40% by screening annually instead of two-yearly and maintaining the current threshold. However, this would require an almost 100% increase in the number of colonoscopies needed. However, changing the interval to three yearly but lowering the threshold to 40 μg/g would achieve a similar saving of lives while only increasing colonoscopies by around 50%.

Conclusions and looking ahead

Endsocopic capacity is the major challenge in restoring and improving the bowel cancer screening programme.

However, repeated use of FIT may better identify at-risk individuals with fewer hospital visits, ensuring that limited colonoscopy and the wider health service is directed towards those at greatest need.

More data is needed to ascertain the safety and effectiveness of such an approach, and researchers for this paper are proposing to conduct further research on the matter.

Contributions and Funding

This study was conducted by researchers from Queen Mary University of London, the London School of Hygiene and Tropical Medicine, the NHS Bowel Cancer Screening Programme (Southern Hub, Guildford), and King’s College London, and funded by the National Institute for Health and Care Research (NIHR).