If endoscopic mucosal resection is so great for large benign colon polyps, why is so much surgery still being done?

Australian investigators, led by Michael Bourke, have made enormous contributions to modern endoscopic mucosal resection (EMR) [1]. In this issue of Endoscopy, Bourke and team applied the size, morphology, site, and access (SMSA) scoring system, which was developed to characterize polypectomy difficulty [2], to their large colorectal EMR database [3]. The SMSA predicted successful complete resection, intraprocedural and delayed hemorrhage, the likelihood of referral for surgery 2 weeks after EMR, and the chance of residual disease at first and second follow-up. The authors proposed six ways that the SMSA could be used in practice ([Table 1]).

Table 1 Potential uses of the size, morphology, site, and access (SMSA) score in clinical practice [3].

Improve informed consent

Improve endoscopy unit planning and resource allocation

Triage lesions with high SMSA scores to EMR referral centers

Improve prediction of need for post-procedure admission

Organize training pathways (target resection of a minimum specified number of lesions in each SMSA category)

Establish case-mix of endoscopist or center for quality assessments

EMR, endoscopic mucosal resection.

“The SMSA is a useful tool and predicts EMR outcomes, but even in the worst outcome SMSA group the overwhelming fraction of lesions are resectable by EMR with good safety and long term cure rates.”

However, as the authors acknowledge, there are limitations to the SMSA because it does not consider certain other factors that are known to affect EMR outcomes. For example, nongranular morphology (not considered in the SMSA) increases the risk of submucosal fibrosis, which makes snare resection during EMR more difficult. Paradoxically, the broadest lesions in the colon are more likely to be granular than nongranular, probably because nongranular lesions turn malignant before becoming very large. Thus, in the current study, 67 % of the group with the worst outcomes (SMSA 4) were granular compared with 54 % of the best outcomes group (SMSA 2). However, granular lesions can generally be removed by EMR regardless of their size, a concept not captured by the SMSA. Similarly, scarring from previous attempts at resection [4] and depressed morphology can affect the difficulty of EMR, suggesting the potential for refinement of the SMSA.

Despite its useful clinical applications ([Table 1]), the SMSA does not fully address the fundamental question facing the therapeutic colonoscopist encountering a laterally spreading lesion (LSL): Do I resect endoscopically or not? The answer to this question lies primarily in whether there are signs of deep submucosal invasion of cancer (ulceration, and disruption of the normal vascular and surface structures [5]), which are specific but not sensitive predictors of endoscopic unresectability. Thus, among the lesions with the worst outcomes (SMSA 4), 93 % of lesions were successfully removed by EMR, 7 % had delayed hemorrhage, 11 % were referred to surgery at 2 weeks, and recurrence rates at 6 and 18 months were 24 % and 10 %, respectively. None of these outcomes preclude attempting EMR in SMSA 4 lesions.

From a broader perspective, it is fair to ask a question beyond the scope of this study: Has the expanding evidence supporting EMR actually transformed large colorectal polyp management in clinical practice? Modern EMR is safer and more cost-effective than surgery for large benign colorectal polyps [6] [7] [8] [9]. In the current study, Sidhu et al. justifiably state “EMR…is now accepted as the standard of care for large (≥ 20 mm) LSLs in the colon” [3]. However, substantial evidence and personal experience indicate that EMR is frequently not the standard practice. Failure to implement EMR routinely for large benign polyps is arguably the largest looming problem in EMR.

In my EMR experience, referrals often come from a small group of surgeons who send patients with benign lesions referred to them for surgical resection. Why are these patients not being referred directly for EMR? Patients travel from other US states to undergo EMR after locating my center on their own, and report that no doctor in their region would consider anything but surgery for their lesion. Some referring physicians refer only patients who are quite elderly or have severe comorbidities. These impressions are consistent with reports of high rates of endoscopic resectability of lesions referred for surgery [10], and with a recent report that rates of surgical resection for benign colon polyps nearly doubled in the US between 2000 and 2014, except in persons in their eighties [11]. This trend could not be attributed to increasing volumes of screening colonoscopy. Persistently high rates of surgery for benign polyps have been reported in the Netherlands [12], and the problem could be widespread.

These data suggest that EMR centers, at least in some countries, see only the tip of a large colorectal polyp iceberg. A generous perspective on the problem enlists lack of endoscopist education, inflexible physician practice patterns, inaccessibility of EMR expertise, and unwillingness of patients to travel to regional centers as potential explanations. A cynical perspective suspects endoscopist unwillingness to acknowledge lack of EMR expertise and refer to other endoscopists, hospitals pressuring physicians to manage cases locally, and surgeons unwilling to surrender a component of their surgical volumes. The mock survey in Table 2 lists potential reasons why patients with large benign polyps are not referred for EMR. Of course, education, biases, skill levels in EMR, and incentives will vary between gastroenterologists and surgical colonoscopists, and vary by region and country. This list of my own making is surely incomplete. I offer it only to stimulate consideration of how to investigate the issue, as understanding the drivers for persistent high use of surgery could inform measures to correct practice toward EMR.

In summary, endoscopic treatment is safer and more cost-effective than surgery for large benign colorectal polyps [6] [7] [8] [9]. The SMSA is a useful tool and predicts EMR outcomes, but even in the worst outcome SMSA group, the overwhelming fraction of lesions are resectable by EMR with good safety and long-term cure rates. Yet, the big picture is sobering, because rates of surgery for benign polyps are stable or increasing [11] [12]. Defining the true barriers to endoscopic treatment of large benign polyps, if possible, could direct development of systems that meet and overcome the education gaps and biases of the various players, moving toward the goal of less surgery and more endoscopic resection of large benign colorectal polyps.

Fig. 1 A mock survey intended to identify biases, education gaps, and incentives underlying referral of endoscopically resectable lateral spreading lesions for surgical resection.

• References

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