Optimizing polypectomy practice: more cutting-edge research needed^[*]

Endoscopists remove millions of colonic polyps each year, and the vast majority of these lesions are small (< 1 cm). Perhaps because of the routine and near monotonous nature of this work, the technical aspects of polypectomy are often accomplished with little thought. A polyp is seen. The snare or forceps is delivered through the working channel to the mucosa. The polyp is removed and, generally speaking, captured for pathologic analysis.

Driven in part by a desire to improve colonoscopy, every aspect of its application is now appropriately coming under scrutiny. Prior studies have clearly demonstrated that, despite our best efforts, colorectal cancer (CRC) can occur within a short interval of a procedure that did not detect cancer [1]. While there are multiple explanations for the failure of colonoscopy to adequately detect or prevent CRC [2], incomplete resection of polyps is an important contributor [3].

“The paper provides further reassurance about the usefulness of cold snare polypectomy for the resection of diminutive and small polyps.”

In this context, the work by Maruoka and colleagues [4] is another step forward in the attempt to optimize polypectomy practice. Measuring the effectiveness of removal of small polyps is challenging because most polyps are never destined to become cancer, so understanding what constitutes adequate resection can generally only be studied on the “micro” (i. e. polyp) level. Often, studies of polypectomy technique use surrogates for complete resection, including the examination of the margins on a path sample or the absence of residual neoplasia when biopsies are taken around the base of a resection margin. However, the presence of edema and/or bleeding after the initial polypectomy may limit the accuracy of such biopsies.

In the current single-arm prospective study, the authors aimed to understand the completeness of resection using cold snare polypectomy for polyps less than 10 mm without relying on pathologic review or immediate post-polypectomy research biopsy. After performing high quality resection techniques to ensure “best effort” at complete removal with a round snare (Captivator II; Boston Scientific), the investigators then deployed a clip to mark the area for subsequent evaluation. They re-examined the site 3 weeks later, both visually and through at least one research biopsy at the scar site to ensure resection adequacy. Guided by the clip, they were able to identify the adenoma site in almost all cases (102/111). Pathologic residual adenoma was found in just one lesion.

The authors should be congratulated for executing this novel near-term prospective assessment of resection adequacy. For diminutive polyps (≤ 5 mm), the results are definitive. Diminutive polyps comprised roughly 80 % of the studied polyps and there was no evidence of recurrence in this group. The sole recurrence occurred in a 7-mm polyp. Unfortunately, there were only 18 small (6 – 8 mm) polyps that were available for assessment. While the absolute risk for recurrence for small polyps was only 5.5 %, the calculated 95 % confidence interval would be quite broad and would include a recurrence risk of about 30 %.

So, what are the primary clinical and research implications for the paper? From a clinical standpoint, the paper provides further reassurance about the usefulness of cold snare polypectomy for the resection of diminutive and small polyps. The practice is safe and effective, particularly for diminutive polyps. But should cold snare polypectomy be the preferred approach for polyps up to 1 cm in size?

To answer that question, definitive comparative effectiveness work is needed. To design such a study, investigators would need to consider the “PICOT” questions that surround the development of research questions [5]. Namely, what populations should be studied and how should the intervention and comparator arms be fashioned? Given the interplay of some of the key considerations, it is likely that multiple well-designed studies will be needed.

For example, the relevant comparators are different for those with diminutive (≤ 5 mm) polyps relative to small (6 – 9 mm) polyps. For diminutive polyps, the most appropriate comparators would be cold snare and jumbo biopsy forceps. From meta-analysis, it is known that these two techniques are superior in terms of resection relative to standard cold biopsy forceps for lesions ≤ 7 mm [6]. The risk of applying electrocautery likely does not justify hot snare polypectomy in patients with diminutive polyps. However, when considering small polyps, the relevant comparators would be hot versus cold snare polypectomy. In fact, one very recent study comparing these two groups head to head has just been reported [7]. Cold snare was found to be non-inferior to hot snare for complete adenoma resection, measured through immediate marginal biopsy. However, two-thirds of the polyps studied were diminutive, so the results are less informative for those with small polyps. Clearly a study specifically powered for small polyps (i. e. no diminutive ones) needs to be designed.

There are other important decisions that would need to be made when designing such studies. Perhaps most important is whether dedicated cold snares should be used for the intervention. One study has suggested that dedicated cold snare devices are superior to more generic snares that can be used either hot or cold [8], but more work in this area would be welcome.

Finally, and perhaps most challenging, in designing this comparative effectiveness work, there is the consideration of endoscopist. Not surprisingly, most of the work in this area has been completed at centers with interested and motivated endoscopists who likely accomplish rates of adequate resection that are higher than those in general practice. While there will always be some artificiality to work completed within the framework of a research trial, the study design should include an expanded number of participating centers and integration of the work into day-to-day practice to the greatest extent possible.

Completion of such high quality comparative effectiveness research will still be only another small step towards optimizing polypectomy practice. Once trials have defined the best tools for polyps of different sizes, work to implement their use effectively into clinical practice will come next. Formal approaches to assessing polypectomy technique are being developed [9] [10] [11]. Choice of appropriate instrument is one of many factors that will require standardized implementation to ensure high quality polyp resection practice. Only through such ongoing clinical and research efforts can we continue to refine the practice of colonoscopy and maximize its benefit in colorectal cancer prevention.

^* This article is in the public domain under U.S. Law

• References

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