Detection of neoplasia at colonoscopy: What next?

 

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The large multicenter European tandem colonoscopy study reported in this issue of Endoscopy reminds us that colonoscopy misses many small and some large polyps and adenomas [1]. The novel observation in this study of greatest value is that the miss rate of flat lesions is higher than that of sessile and pedunculated lesions. This result has not been previously tested directly in a tandem study [2] [3] [4] [5] [6], though other study designs have suggested it [7] [8] [9] [10] [11] [12] [13] [14]. Two findings in the study should be viewed with suspicion. First is that multiple polyps at baseline predict a lower miss rate. Other studies have found the opposite result [3] and in postpolypectomy surveillance studies patients with three or more adenomas at baseline consistently have an increased risk of advanced adenomas at follow-up [15]. The explanation is certainly (at least in part) that the greater the number of adenomas the patient has, the greater the opportunity that one or more will be missed. Second, the observation that left-sided lesions are more likely to be missed also runs against findings of previous miss rate studies [2] [3] [4] [5] [6] as well as the observation that interval cancers tend to cluster in the right colon [16] [17]. To their credit, the authors recognize these inconsistencies between their own and previous findings.

The bigger problem with colonoscopy and polyp detection is not that it misses some polyps, nor that it misses more polyps on one side of the colon than the other, etc., but rather that the rate of missing is so dependent on the operator. When I think of a model to which colonoscopy might aspire, I often think of commercial aviation. When we step onto a commercial air flight we are randomly assigned to the care of a pilot whom we have never met, who takes us on a journey that is potentially fatal, but which is performed with a success and safety rate of almost 100 %. The success and safety rate are so high that we correctly assume, without question, the competence of the pilot. Similarly, our patients generally assume the competence of their colonoscopist and the protective value of colonoscopy. If they understood the situation better, they would discard those assumptions.

For example, the 21 % miss rate of adenomas in the current study is the mean miss rate of many colonoscopists, some with lower and others with higher miss rates (this data was not shown). Variation in detection has been found in every study that has looked for it [3] [18] [19] [20] [21] [22] [23]. The level of variation can be staggering [18] [19] and it extends to the detection of large adenomas [18] [19]. In two large series, it is evident that the lowest level performers missed considerably more than half the large (> 1 cm) adenomas in the colon [18] [19]. In the current study, the authors reassure us that they limited bias as related to “operator expertise” by employing study colonoscopists with “extensive experience”. Unfortunately, we already know that experience as defined by performing a lot of colonoscopies is not a reliable predictor of high level adenoma detection [3] [18] [19] [20] [21] [22] [23]. Preliminary data demonstrating adequate adenoma detection by the individual endoscopists would be reassuring, but “experience” is not. The point is that the only way to identify competent adenoma detectors is to measure adenoma detection and that competence in adenoma detection may not correlate with numbers of colonoscopies performed, high cecal intubation rates, or a reputation for skill at therapeutic colonoscopy.

Much research is ongoing into technical advances that may improve adenoma detection. For example, chromoendoscopy improves detection of small flat lesions but is impractical for routine use [24]. Narrow band imaging is more practical than chromoendoscopy and is a useful learning tool for identification of flat lesions [25]. Narrow band imaging does not improve adenoma detection for high level adenoma detectors in white light [26], which is no surprise to the experienced NBI user who knows that nearly every adenoma seen in NBI remains visible when viewed in white light. High definition optics appear promising [26] but have not been directly tested for an effect on detection of flat lesions. Methods to see the proximal sides of folds better include wide-angle optics [27], cap or hood-fitted colonoscopy [28] [29] [30], and the Third-Eye Retroscope [31]. Wide-angle optics produce an operator-dependent improvement in efficiency but are not a fix for missing adenomas [27]. Cap-fitted colonoscopy shows promise [28] [29] [30] and both cap-fitted colonoscopy and the Third-Eye Retroscope are under investigation. While several of these tools appear to have the potential to make real contributions to detection and at the same time be practical enough to actually use, it seems unlikely that they will replace the need for high level performance by the operator; i. e. colonoscopy is likely to remain operator-dependent.

There are simple measures that all colonoscopists can take right now to improve neoplasia detection. “Split-dose” bowel preparation (the patient takes half the preparation on the day of the colonoscopy) has emerged as a useful contributor to polyp detection for both sodium phosphate and polyethylene glycol preparations [32] [33] [34]. Mucosal inspection should be allotted sufficient time [35] and the time taken should be recorded for every patient [35]. Intubation of the cecum should be properly documented and photographed [35]. Inspection during withdrawal should entail compulsive interrogation of the mucosal surfaces on the proximal sides of folds, flexures, valves, turns, etc. Finally, we must measure our individual adenoma detection rates [35]. Overall adenoma detection correlates with large adenoma detection, and is the primary measure of the quality of mucosal inspection [35].

When a patient presents for colonoscopy, they generally hope for several things, including a comfortable examination free from perforation, but the long term goal is to avoid colorectal cancer and death from a largely preventable disease. We colonoscopists could view ourselves as the pilots on a journey to prevent colorectal cancer. The tandem study reported here reminds us that colonoscopy is imperfect at neoplasia detection. It is time for us to bring the lessons of the miss-rate literature home to our individual practices. Until each of us knows our individual adenoma detection rate and views it as a measure of competence, we cannot know whether we are good and safe pilots.

Competing interests: None

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D. Rex, MD 

Indiana University Hospital
Department of Medicine, Division of Gastroenterology and Hepatology

550 N. University Blvd. IU Hospital
4100 Indianapolis 46202
United States

Fax: +1-317-274-5449

Email: drex@iupui.edu