The polyp-cancer sequence means that appropriately timed colonoscopy could dramatically reduce both colorectal cancer (CRC) incidence and mortality by detecting and completely removing conventional and serrated adenomas, from which the majority of CRC arises. To maximise this potential benefit, colonoscopy must be performed to a very high standard at appropriate intervals.
The number of colonoscopies performed annually in Australia is fast approaching one million; if these procedures were all directed towards 50 to 80 year olds, each Australian in that age group could already have a colonoscopy performed every 8 years. However, data also show that there is enormous geographic disparity among annual rates of colonoscopy per head of population. Despite incidence and mortality statistics trending towards improvement, even greater favourable trends might be expected, given the high volume of colonoscopy in Australia. These findings suggest that we could be doing better when it comes to technical performance of colonoscopy, and compliance with national guidelines on indications for the procedure, including timing of surveillance procedures.
As was the case when these guidelines were last updated in 2011, the current update has had to rely on evidence from studies that included colonoscopies performed more than a decade ago. In the interim, the technical quality of colonoscopes has increased dramatically and the care with which these instruments need to be used has attracted more and more attention. Thus, extrapolating from the available literature to generate reasonable recommendations remains as difficult now as it was in 2011.
Over the same time period, it has become even clearer that colonoscopy is far from perfect; that it is less protective against post-colonoscopy cancers in the proximal (right) colon than in the distal (left) colon and that, even on the left side, colonoscopy is nowhere near completely protective against subsequent CRC development. It is now established that fewer interval CRCs develop among the patients of proceduralists with higher adenoma detection rates. Given that colonoscopy currently provides limited protection against CRC in the right colon, attention needs to be given to the sessile serrated adenoma detection rate, which is an emerging indicator of colonoscopy quality. Of course, detection alone is not enough. Whether detected lesions are conventional adenomas or sessile serrated adenomas, colonoscopy is only protective if polypectomy is complete.
Colonoscopy is only protective if polypectomy is complete. It is therefore incumbent upon every colonoscopist not only to maintain, but to improve their diagnostic and therapeutic skills, to be able to practise ‘modern’ high-quality colonoscopy.
As guidelines, the recommendations regarding surveillance intervals outlined in this document cannot be applied rigidly to each and every patient. Bowel preparation, for instance, may be suboptimal, interval symptoms may develop, or repeat procedure intervals based on a strong family history of CRC may take precedence over a surveillance interval dictated by a person’s latest colonoscopy findings. Nevertheless, the guidance based on this up-to-date, evidence-based literature review will allow clinicians to better manage not only individual patients, but also colonoscopy waiting lists, and help balance the greater urgency of colonoscopy for symptomatic patients and those with positive immunochemical faecal occult blood test at screening (including National Bowel Cancer Screening Program participants) against the urgency of surveillance colonoscopy procedures.
Dr Cameron Bell
Chair, Surveillance Colonoscopy Guidelines Working Party