Intermediate Adenomas and All Adenomas research summary

Overview

The Intermediate Adenomas (IA) study aimed to assess the recommendation of the 2002 UK post-polypectomy surveillance guidelines that intermediate-risk patients required 3-yearly surveillance colonoscopies.

In 2017, we received additional funding to assess the guideline recommendations for those classified as low- and high-risk. As this was in addition to the intermediate-risk group previously investigated this became known as the All Adenomas (AA) study.

This trial is registered with the ISRCTN Clinical Study Registry. Its unique number is 15213649.

Background

Colorectal polyps can develop into cancer, which means they are removed at colonoscopy to reduce an individual’s chance of developing colorectal cancer. However, depending on the characteristics and number of polyps, some patients remain at a higher risk of developing colorectal cancer and will benefit from colonoscopic surveillance. This surveillance was defined in the 2002 UK post-polypectomy surveillance guidelines. These guidelines classified people with adenomatous polyps into low-risk, intermediate-risk or high-risk groups depending on the characteristics of their adenomas and recommended differing levels of surveillance. However, these guidelines had not been updated since their development in 2002 and needed to be re-examined. Surveillance colonoscopy is expensive, uncomfortable and carries a small but real risk of serious complications for patients. It was therefore essential that surveillance colonoscopies were directed towards people who need and benefit from surveillance the most.

The IA study aimed to provide robust evidence to underpin revisions of the 2002 UK guidelines. It focused on people who were classified as intermediate risk and were recommended to have three yearly surveillance colonoscopies. This group accounted for the majority of surveillance colonoscopies in the UK. We hypothesised that this was likely an appropriate regime for some in the intermediate-risk group, but that others may not need three yearly surveillance. We also aimed to examine the psychological impact of having surveillance on patients, and costs of surveillance to the NHS.

The AA study extended these analyses, including an examination of the appropriateness of the 2002 UK guideline recommendations for people in the low-risk and high-risk groups, to provide further evidence to support an update of these guidelines. We also aimed to investigate the cost-effectiveness of surveillance for each risk group.

Method

Both the IA and AA studies were observational retrospective cohort studies that utilised routinely collected data on health examinations performed in the past.

Medical data was collected on over 250,000 people who had previously had a colonoscopy at one of 17 participating hospitals between 1972 and 2010. Of these, 30,000 men and women with adenomatous polyps were included in the studies. We obtained data on cancer diagnoses and deaths from the NHS Central Register, NHS England, and the NHS National Services .

Results and impact

The results from the IA and AA studies played a key role in the development of the new 2020 UK post-polypectomy surveillance guidelines.

The IA study showed that most intermediate-risk patients derive benefit from having a surveillance colonoscopy. However, we determined that approximately 25% of the intermediate-risk group were at low risk of developing colorectal cancer after polypectomy and before any surveillance, indicating that surveillance might not be warranted for this ‘lower-risk’ subgroup. These findings were published in The Lancet Oncology and the NIHR-HTA Journals Library in 2017.

The AA study demonstrated that patients classified into the low-risk group are very unlikely to develop colorectal cancer after polypectomy and so do not need any surveillance. Our updated analyses of the intermediate-risk group corroborated our finding from the IA study that a ‘lower-risk’ subgroup of intermediate-risk patients exists that could be withdrawn from surveillance. Finally, we showed that surveillance is necessary for high-risk patients who remained at increased risk of colorectal cancer after polyp removal. These findings were published in the journal Gut in 2021 and in the NIHR-HTA Journals Library in 2022.

Together, our findings demonstrated that some post-polypectomy patients do not require the level of surveillance recommended in the 2002 UK surveillance guidelines. The findings played a key role in the development of the new 2020 UK post-polypectomy surveillance guidelines endorsed by the British Society of Gastroenterology, the Association of Coloproctology of Great Britain and Ireland, and Public Health England.

The updated post-polypectomy surveillance guidelines are helping to optimise the use of NHS resources, ensuring patients at high risk of colorectal cancer receive surveillance and are protected, while minimising exposure of low-risk patients to unnecessary invasive procedures.