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Colorectal cancer rates after colonoscopies too varied

Thousands of cases missed by testing failures

Adrian O'Dowd

Thursday, 14 November 2019

A study has revealed that substantial variation exists between colonoscopy providers in rates of colorectal cancer up to three years after colonoscopy in England.

The study* published by The BMJ today showed that although the rates of post-colonoscopy colorectal cancer have significantly reduced and are now amongst the lowest rates globally, there are worrying variations across the country between providers with some three times as likely to miss signs of cancer as others.

Colorectal cancer is a significant public health problem in the UK, with more than 40,000 new cases diagnosed and 16,000 deaths each year.

As the main test for colorectal cancer, colonoscopy is not always 100% accurate and cancers can appear within months or years after a negative result – called post-colonoscopy colorectal cancers or PCCRCs.

The British Society of Gastroenterology says PCCRCs should be used as a benchmark for the quality of a colonoscopy service, and the World Endoscopy Organisation (WEO) has recently developed a way to compare performance between providers.

Using this method, a team of UK researchers led by the University of Leeds set out to compare PCCRC rates between all providers in England to measure variation in colonoscopy quality.

Their findings were based on 126,152 individuals undergoing colonoscopy in England between 2005 and 2013 and subsequently diagnosed with colorectal cancer.

The proportion of those diagnosed six months to three years after the colonoscopy were identified to calculate a PCCRC-3yr rate.

Results showed that in England during this nine-year period, 9,317 bowel cancers were either not detected or not prevented.

After taking into account potentially influential factors such as age, sex, and medical history, the PCCRC-3yr rate declined from 9% in 2005 to 6.5% in 2013.

However, rates for colonoscopies performed within the NHS Bowel Cancer Screening Programme were better (meaning lower) at 3.6% than those performed by independent providers (9.3%), who are increasingly being used to meet the rising demand for colonoscopy

The researchers claimed that if this lower rate (3.6%) had been achieved over the entire study period, more than 3,900 cases of colorectal cancer could have been prevented or diagnosed earlier.

Given that this was an observational study, it could not establish cause and the researchers acknowledged some limitations in the data, which may have affected the accuracy of the calculations.

Nevertheless, they said this was a large, nationally representative study, and the variation between providers remained after further analyses, suggesting that their findings withstand scrutiny.

They concluded: “PCCRC is largely avoidable and targeted improvement is required to reduce this variation and drive down PCCRC-3yr rates further. This will result in earlier diagnosis and improve mortality from this preventable disease.”

Dr Lisa Wilde, director of research and external affairs at Bowel Cancer UK said: “It is clear from the research that variation between colonoscopy providers in England must be reduced.

“Whilst it’s encouraging that there has been some improvement, the research suggests that between 2005 to 2013 almost 4,000 bowel cancers could have been prevented or diagnosed earlier if colonoscopy providers matched the lowest rates of post colonoscopy colorectal cancers seen in the study.

“Recognising and highlighting variation in colonoscopies is key, but research is needed to understand why this variation is happening.”

*Burr N E, Derbyshire E, Taylor J, et al. Variation in post-colonoscopy colorectal cancer across colonoscopy providers in the English National Health Service: population-based cohort study. BMJ 2019;367:l6090. DOI:10.1136/bmj.l6090.

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