Individually assessing a patient's risk beats rigidly adhering to screening intervals, say experts.
The recent guideline change that pushed surveillance colonoscopies from five to 10 years after polyp removal is putting patients at “unacceptable” risk, according to Australian research.
The 2019 update to the clinical guidelines was intended to help clinicians balance “the greater urgency” for symptomatic patients and those with positive immunochemical faecal occult blood tests against that of surveillance procedures, the taskforce said.
But an analysis of 960 South Australian patients who had previously had non-advanced/low-risk adenoma found that neither size nor location of the initial non-advanced adenoma influenced the incidence of advanced neoplasia at follow-up – but interval time did.
“The incidence of advanced neoplasia increased with time between adenoma removal and the surveillance colonoscopy, from 13% (2.0–3.9 years after polypectomy) to 32% (eight or more years),” the authors wrote in the MJA.
They found patients were more likely to develop advanced neoplasia if they were older when the polyp was removed, had a prior history of adenoma, or had two polyps (compared to one) at their initial procedure.
“We estimated that the incidence of advanced neoplasia following removal of non-advanced adenoma was 19% at five years and 30% at 10 years …. Increasing the colonoscopy surveillance interval from five to 10 years would therefore increase the incidence of advanced neoplasia at surveillance by 60%.”
Nevertheless, the authors acknowledged that the guideline update said the surveillance intervals should not be applied rigidly in every case and stressed the need to consider the quality of the initial colonoscopy, patient risk factors and results of other investigations such as interval faecal immunochemical tests.
Dr Karen Barclay, colorectal surgeon and co-author of the 2019 guidelines, echoed this point when defending the guidelines to InSight+.
“Really, the guidelines are not just saying ‘do it at 10 years’. They’re actually saying to consider what you’ve found. Consider this person in the context of who they are in this environment right now and make a recommendation based on that. Not a blanket statement.”
Advanced neoplasia can be diverse and did not necessarily mean patients would develop cancer, she added.
“If you’re just taking this on face value, what does it actually mean? It means that of all the people who have a colonoscopy, this proportion, the lowest risk of the lowest risk, a number of them might get something that over five, 10 or 20 years might become a problem.
“We’re not saying that 30% of the whole population is going to get colorectal cancer.”
Aside from surveillance, it was also important to talk with patients about ways they could minimise their risk of developing further adenomas, she said.