Bowel cancer after a ‘clear’ colonoscopy
A colonoscopy is a test which uses a small thin tube with a camera to look inside your bowel. As well as being the main diagnostic test to detect bowel cancer (also called colorectal cancer or CRC for short), colonoscopies can also prevent cancer by enabling the removal of pre-cancerous polyps (called lesions).
As patients, we assume that a colonoscopy will always detect any cancer and any pre-cancerous lesions. However, they are not always that easy to spot and remove completely. Tumours and polyps can look different in each patient and at different stages of their growth or be obscured from the view of the camera.
When people are thought to be at risk of future cancer after having a large polyp removed or because they have many polyps in the bowel, repeat tests are booked and sometimes these are not performed. Some cancers can also grow very quickly and may not have been present at the initial test. So, despite having had a colonoscopy, some patients go on to develop bowel cancer – referred to as post-colonoscopy colorectal cancer (PCCCRC). These cancers tend to have poorer outcomes as the earlier the cancer is identified the more successful the treatment is likely to be.
Dr Nick Burr and his colleagues in the UK Colorectal Cancer Intelligence Hub, led by Professor Eva Morris, worked to understand how many people in England have been diagnosed with these cancers and whether this varies in different parts of the country.
What did the research find?
Dr Burr looked at data about bowel cancers that had been diagnosed in England between 2005 and 2013. If any of these cancers had been diagnosed within three years after the patient had a colonoscopy, then it was classed as ‘post-colonoscopy’ cancer.
They showed that over time, there was a reduction in the rates of these cancers in England which is likely to reflect an improvement in the quality of colonoscopy tests. However, there were still significant variation across different colonoscopy ‘providers’ in England. Encouragingly, tests that were done as part of the NHS’s Bowel Cancer Screening Programme, tended to have the lowest rates.
If all the colonoscopy providers had post-colonoscopy cancer rates equal to the providers with the lowest rates, then over the nine years the study covered, up to 3,900 bowel cancers might have been diagnosed earlier or even prevented.
What is the impact on patients?
Patients will benefit from this sharing of data because:
- There will be an increased emphasis to establish ‘best practice’ from those best performing providers and to see that best practice implemented in those that have not performed so well.
- The research defined those categories of patients most at risk of PCCRC such as previous cancers, inflammatory bowel disease and diverticular disease. Increasing awareness of these groups has the potential for even more cancers to be diagnosed earlier or even prevented.
- Bowel Cancer UK has funded a further piece of research, led by Professor Eva Morris, which will identify cases of undetected cancer going forward and ask the hospital where it occurred to review these cases in detail. This review process will help the hospital to understand what happened and why the cancer may have been undetected. Professor Morris and her colleagues can then look at all the cases across all the hospitals to identify the most common reasons for bowel cancers not being detected at the time of a colonoscopy.
What data was used?
The UK Colorectal Cancer Intelligence Hub has developed a large, secure research data system known as the UK Colorectal Cancer data Repository (CORECT-R). It contains de-identified data about diagnosis, treatment and outcomes from patients who have had bowel cancer. De-identified data is data that does not identify an individual patient, because any identifiable data been scrambled or removed. The data is provided by Public Health England who is allowed to share NHS healthcare data which has been de-identified but only for ‘improving health, care and services through research and planning’.
As a cancer patient who still has colonoscopies, I feel that I want to find out how my local provider has performed. However, much more importantly, I want to have confidence in knowing that my local provider is following any revised ‘best practice’ that can be established.Pete Wheatstone, Bowel Cancer UK and DATA-CAN PPIE groups
Who funded and collaborated on this work?
This work was funded by the Bobby Moore Fund, Cancer Research UK, Yorkshire Cancer Research, and Crohn’s and Colitis UK.
Bowel Cancer UK
British Medical Journal