Over 35,000 people are diagnosed with colorectal cancers in England each year, with the majority of cases detected through NHS colonoscopy services. Detecting cancer early is critical to improving treatment outcomes and long-term survival, making it vital to understand and address why some cancers are missed.  

Up until now, reviews of post-colonoscopy cancers in England have often been inconsistent and incomplete. A new national audit, funded by Bowel Cancer UK, Cancer Research UK, Health Data Research UK (HDR UK), and the NIHR Oxford Biomedical Research Centre, has established the first standardised national system for identifying and analysing post-colonoscopy colorectal cancers (PCCRCs). 

Published in Endoscopy, the research represents the largest and most detailed review of PCCRCs ever undertaken. It analysed 1,724 cases across 126 NHS hospitals in England, finding that two-thirds of cases were categorised as possible missed cancers, even when the colonoscopy quality had been deemed adequate. Over four in ten  (44%) of patients experienced harm due to delayed diagnosis — including premature death in 8% of cases. Certain areas of the bowel were higher risk – PCCRCs were more common in harder-to-examine regions, such as the transverse colon and the hepatic and splenic flexures.   

A data-driven national audit 

By linking cancer registry and hospital records, researchers were able to capture cases even if the patient had the original colonoscopy and got their diagnosis at different hospitals. Local clinical teams then reviewed each case using a standardised framework which aligned with international best practice.  

The research was led by Dr Nick Burr, Consultant Gastroenterologist at Mid Yorkshire Teaching Hospitals NHS Trust, and the senior author was Professor Eva Morris, Professor of Health Data Epidemiology at Oxford Population Health and a researcher supported by HDR UK’s Big Data for Complex Disease (BDCD) Driver Programme. The BDCD programme brings together experts across the UK to harness large-scale, linked health data to better understand and tackle complex diseases, including cancer. 

Professor Eva Morris said: 

“The NHS is uniquely positioned to find and tackle these missed cancers because it generates incredibly rich datasets. Their linkage and use enables this study’s audit system to simply and efficiently identify all PCCRCs and by learning from each and every case, set new standards, strengthen training, make colonoscopy safer and, most importantly, diagnose cancer earlier, or even prevent it, for hundreds of people each year.  

“This simple, data driven approach, could not only save valuable resource but also many, many lives. Unfortunately, whilst we’ve shown this approach is successful in improving diagnostic services it is not yet routine clinical practice in the NHS. This is a huge missed opportunity to help, cost effectively, improve cancer outcomes. We can, and should, be doing more with NHS data to save lives.” 

Turning evidence into action 

The study identified several areas where service improvements could reduce the risk of missed cancers: 

  • Ensuring better bowel preparation and repeat testing where initial procedures were incomplete. 
  • Expanding training and referral pathways for complex polyp removal. 
  • Improving photo documentation, with audits of image quality for colonoscopy quality. 
  • Providing closer monitoring for high-risk groups, such as patients with inflammatory bowel disease, Lynch syndrome, or a history of bowel cancer or polyps. 

Dr Nick Burr said: 

“This is the largest study of its kind, and it shows clearly that most of these cancers could have been avoided. The audit gives us the evidence we need to improve services, prevent harm, and ultimately save lives.” 

Real-world impact 

It is estimated that around 1,200 PCCRCs occur in England each year. Acting on these findings could prevent or enable earlier diagnosis for over 800 of these cases annually — reducing the burden on NHS cancer services and improving outcomes for patients. 

Rachel James, who has Lynch syndrome, a genetic condition that can increase the risk of bowel cancer, and was later diagnosed with cancer following a false-negative colonoscopy, said:  

“On the one hand I feel incredibly lucky, knowing that I have Lynch syndrome and the fact that I was on the bowel cancer screening program did mean that following successful surgery, and amazing support from the endoscopy team at North Tyneside General Hospital, I was cancer free. But the impact this has had on us all as a family, the waiting on test results, the recovery, and my own quality of life post-surgery as well as the cost to the NHS has been significant.  

“It is frustrating that this could have avoided and it worries me that I’m back on two yearly screening colonoscopies when clearly this wasn’t enough, if I get bowel cancer again the outcome will certainly be worse. I have heard of so many people in similar situations that haven’t had as positive an outcome as I have had and while we say in the Lynch community that knowledge is power, there is little point knowing you have Lynch if the screening programs aren’t fit for purpose.” 

Read the full paper and find out more about the study from Oxford Population Health. You can also read more about HDR UK’s Big Data for Complex Disease (BDCD) Driver Programme.