A “vision” for fast snaring: please take your timeReferring to von Figura G et al. p. 45–51
18 December 2019 (online)
Data from retrospective studies indicate that most interval cancers result from either missed or incompletely resected lesions during previous examinations. Additionally, a very small proportion may be attributed to de novo cancers. In this context, a number of different techniques, technologies, and devices have so far been studied with the aim of improving colonoscopy outcomes, with varying results . Among these, the Endocuff device (Arc Medical Design, Leeds, UK) and its descendant the Endocuff vision device (EVD; Norgine Pharmaceuticals Ltd, Uxbridge, UK) – devices mounted on the tip of the scope with flexible projections that aim to flatten the mucosal folds and facilitate inspection – have been extensively studied. Two studies have shown that compared with standard colonoscopy, Endocuff use is associated with a lower adenoma miss rate , and the most recent meta-analysis revealed a significant, albeit small, benefit in terms of the adenoma detection rate (ADR) with Endocuff-assisted colonoscopy; this benefit was restricted to endoscopists with an ADR lower than 35 % .
“...given the faster insertion and polypectomy times owing to the hypothesized ease of snare positioning, one would expect to see higher levels of endoscopist satisfaction in the EVD arm, but this was not detected.”
At this point, we must congratulate Dr. Guido von Figura and his colleagues for taking a step forward to explore the utility of this add-on device by conducting an elegantly designed prospective, randomized study to examine whether use of the EVD can accelerate the resection of colonic polyps . The authors randomized 250 patients to undergo either EVD-assisted or standard colonoscopy, which was performed by 14 endoscopists inexperienced in use of the EVD. The primary outcome was the median duration of polypectomy, defined as the time needed from insertion of the first polypectomy device (e. g. forceps, snare, or injection needle) into the scope until the polyp was resected. The investigators showed that the use of the device significantly reduced the median duration of polypectomy by > 30 % (from 80 to 54 seconds; P = 0.02), almost meeting their study power analysis target, which was to reduce the polypectomy time by 33 %, although the absolute values of the targets were completely different from those actually achieved. Interestingly, EVD-assisted polypectomy was faster only for polyps that measured > 6 mm, while this benefit was not detected for the resection of diminutive lesions.
Among the secondary endpoints were a shorter total colonoscopy duration with the EVD (23 vs. 27 minutes; P = 0.02) in the absence of any difference in withdrawal times between the two arms (more than 6 minutes), and a lower number of polyps requiring more than one resection in the intervention group, thereby indicating facilitation of the procedure when the device was used. At the same time, cecal intubation was faster, in line with the literature , and the study was not powered to detect differences in terms of the ADR.
It is a common feeling, albeit not proven, among endoscopists using Endocuff in clinical practice that the scope is more stable during its withdrawal when this device mounted on its tip; this fact may explain the study results. However, polypectomy is not a standardized technique: it is operator dependent and variability in the endoscopistsʼ technique and skills are critical to assure effective polypectomy. Moreover, the time taken for careful inspection of the polypectomy site, which is of paramount importance to avoid adenoma recurrence, was not included in the study endpoints. Unfortunately, the authors did not examine the completeness of polypectomy and, although they involved “experienced” endoscopists (does a record of > 150 colonoscopies guarantee adequate experience and efficiency?), the rate of incomplete polyp excision is known to vary widely, even among experienced endoscopists .
Beyond the aforementioned limitations, along with the inherent inability of a study like this to mask the scope from the operator and the unknown attitudes and preferences of the participating endoscopists towards EVD use, there are several other issues to discuss in order to accurately interpret the value of this study. Looking at the authors’ Table 1s, it is unlikely that many polyps larger than 20 mm (even larger than 15 mm) were resected during the study. Consequently, I hesitate to extrapolate the time-saving effect seen with the use of EVD-assisted colonoscopy when resecting relatively small lesions to a similar effect for the excision of larger lesions, especially if large piecemeal endoscopic mucosal resection (EMR) is required. Moreover, the rate of polyps that were not retrieved after excision is high for a clinical study; to exclude the possibility that EVD contributed to an inability to retrieve excised polyps, it would be of value to know the distribution of these polyps among the two study arms. Another missing piece of information is the number of failed attempts to correctly position the snare, which would be a different way of evaluating the impact of the EVD on polypectomy. Finally, given the faster insertion and polypectomy times owing to the hypothesized ease of snare positioning, one would expect to see higher levels of endoscopist satisfaction in the EVD arm, but this was not detected.
One may also argue about the clinical relevance of a 26-second and 4-minute reduction in polypectomy and overall colonoscopy times, respectively, but considering the increasing burden on endoscopic facilities, especially for colorectal cancer (CRC) screening and surveillance, a gain of two or three more examinations being performed per day in a busy facility might outweigh the cost of the device and may decongest patient waiting lists. However, by recommending, for example, screening only for individuals with a 15-year CRC risk higher than 3 % – African Americans excluded –  and by loosening the surveillance schedules for those with low risk index adenomas , we might resolve the paradox of offering more to those benefiting less from colonoscopy, and this approach might represent a better rationalization of colonoscopy service provision for society than trying to find new roles for add-on devices.
Our German colleagues made a big step forward with their study! However, speed is not an issue in endoscopy and the “vision” of fast snaring can wait until it is proven that acceleration does not compromise the completeness of polypectomy, even for large lesions. Therefore, I will continue to take my time to examine the polyp, to correctly place the snare, to snare the polyp, and to inspect the excision site for any remaining adenoma.
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