Lumen-apposing covered self-expandable metal stents for short-length gastrointestinal strictures: Will they take hold?

Benign strictures can occur throughout the gastrointestinal (GI) tract. Endoscopic therapy consists primarily of dilation with or without fluoroscopy. For esophageal and rectal strictures, this consists of balloon dilation and over-the-wire rigid (bougie) dilation. At other locations within the GI tract, through-the-scope balloon dilation is used. Endoscopic dilation is usually effective, though some patients may require one or more sessions to achieve an adequate response. Unfortunately, in a subset of patients, repeated dilation sessions are ineffective in maintaining an adequate lumen. Such refractory strictures are problematic, as there are few remaining options, and surgery is not often a simple matter in these patients. Electroincision is effective for short anastomotic and nonanastomotic strictures. Intralesional corticosteroid injection may have some efficacy in peptic esophageal strictures and inflammatory bowel disease-related strictures, but the outcome in short, anastomotic strictures often seems to benefit the endoscopist more than the patient, though it is often used as adjuvant therapy owing to its low risk and relatively low cost.

“It is reasonable to consider the use of LAMS for patients in whom all other endoscopic interventions have failed.”

The use of covered self-expandable stents (SEMS) for management of benign GI strictures emerged about 15 years ago, though their use remains off-label in most countries, including the United States. The initial enthusiasm for fully covered SEMS in the management of refractory strictures has dampened over the years, primarily because of high migration rates, but also because of poor efficacy in many trials. Although migration can be reduced (but not eliminated) by anchoring using endoluminal sutures [1] [2] or over-the-scope clip placement [3] [4] [5], these adjuvant therapies add additional, often nonreimbursable and substantial cost, and also prolong the procedure time. For rectal locations, anchoring at the distal side may not be effective, as the stents need to be anchored on the proximal side, which is technically more difficult because the devices need to be passed through the stent lumen, potentially causing stent dislodgment. Additional problems include stent placement for strictures located at anastomotic sites not situated proximally to an intact pylorus, such as Roux-en-Y gastrojejunostomies – situations in which distal migration into the small bowel could cause downstream bowel obstruction requiring surgical intervention.

Lumen-apposing metal stents (LAMS) are of short length (1 cm) with large flanges. Currently, the largest mid-body diameter of the most commonly used stent (Axios; Boston Scientific, Marlborough, Massachusetts, USA) is 15 mm, though it is anticipated that a 20 mm stent will soon become available. LAMS were designed to anchor together two lumens not normally apposed. However, preliminary series have shown that these stents are useful for short benign strictures (< 1 cm). Advantages of LAMS are the short distance between the flanges (1 cm) and the large diameter of the flanges, which essentially “sandwich” the stricture and probably account for the low rate of migration. The Axios stent is designed specifically for passage through an echoendoscope; the delivery system attaches directly into the Luer-Lok fitting of the proximal working channel, allowing the endoscopist to deploy the stent without assistance. The endoscopic view provided by an oblique echoendoscope (the ultrasound functionality of the scope is not necessary for luminal placement) can be slightly awkward; however, the stent can also be used with therapeutic channel, forward-viewing upper endoscopes (and even duodenoscopes), for which the delivery system is excessively long and requires support. Thus, the deployment in these cases is similar to other stents, where an assistant is vital in device deployment. Notably, one endoscope manufacturer produces a forward-viewing linear echoendoscope with which Axios stent placement for strictures can easily be performed by the endoscopist without assistance (also without the use of the echo portion of the endoscope). Placement of these stents is not fluoroscopy dependent (other than ensuring proper wire passage in difficult cases) owing to the short stent length and ease of precise endoscopic visual placement (especially when forward-viewing scopes are used). Stent removal is relatively easy using grasping forceps.

In this issue of Endoscopy, Yang et al. [6] provide results of a retrospective multicenter study of 30 patients who underwent successful LAMS placement for short-length (4 – 5 mm) strictures, of which nearly 90 % were (not unexpectedly) anastomotic, and most were gastrojejunal. Of the 30 patients, 27 had undergone previous multiple endoscopic therapies, including traditional SEMS placement prior to undergoing LAMS placement. LAMS migration occurred in 8 % of patients. Approximately 83 % of patients were symptom free at 100 days following stent removal. These results are substantially better than previous reports using fully covered SEMS for benign GI strictures, including a large series using LAMS from our centers, which showed a clinical success at 6 months of 61 % [7]. This may be due to a shorter median follow-up in the Yang paper. Additionally, and somewhat surprisingly, two severe early adverse events occurred – one patient with bleeding that required embolization and one patient experienced perforation that required surgical repair. It was unclear whether pre- or postdeployment dilation had been performed during placement in either of these two patients, as dilation was performed in some patients in the series even though the delivery system (10.8 Fr in diameter) should easily pass through a small (~4 mm) stenosis.

Other series, one describing 5 patients [8], and another with 25 patients (including patients from our own centers) [7], have been published using the same device for the same indications. However, we noted some problems not described in the present series, including de novo strictures and buried stents, the latter presumably due to strictures incorrectly measured at less than 1 cm in length. Whether other LAMS (SPAXUS; Taewoong Medical, Seoul, Korea) or short-length (2 and 3 cm), flanged stents (e. g. Nagi Stent; Taewwoong Medical), both available outside the United States, yield similar results in such strictures remains to be seen.

The basic hypotheses being tested in these studies – that short anastomotic strictures are more amenable to prolonged stent therapy than longer benign strictures, and that a wide, dumbbell-shaped stent can largely prevent migration – seem valid. The authors do not define a timeline for what they considered long-term clinical success. One must certainly be cautious about interpreting the results of this study as a potentially good long-term solution, given the short median follow-up of only 100 days after stent removal.

Will LAMS become the endoscopic treatment of choice for patients with this type of stricture? The answer is a qualified maybe. First, the devices are not universally available. Second, their cost is much greater (up to five times more) than that of traditional covered metal stents. More importantly, larger numbers of patients enrolled in randomized controlled trials comparing these devices with traditional therapy with much longer follow-up (perhaps years) are needed. At the present time, however, it is reasonable to consider the use of LAMS for patients in whom all other endoscopic interventions have failed (multiple dilations with or without corticosteroid injection, needle-knife electroincision) as a final endoscopic therapy before consideration of surgery, and perhaps even as destination therapy in poor surgical candidates. As management of these patients continues to evolve, studies should address the most appropriate duration of stent therapy, and whether a more tailored approach based on a wider range of LAMS sizes and shapes can further improve upon long-term patency of refractory anastomotic strictures.

• References

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• 2 Ngamruengphong S, Sharaiha RZ, Sethi A. et al. Endoscopic suturing for the prevention of stent migration in benign upper gastrointestinal conditions: a comparative multicenter study. Endoscopy 2016; 48: 802-808
• 3 Diana M, Swanström LL, Halvax P. et al. Esophageal covered stent fixation using an endoscopic over-the-scope clip. Mechanical proof of the concept and first clinical experience. Surg Endosc 2015; 29: 3367-3372
• 4 Mudumbi S, Velazquez-Aviña J, Neumann H. et al. Anchoring of self-expanding metal stents using the over-the-scope clip, and a technique for subsequent removal. Endoscopy 2014; 46: 1106-1109
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• 6 Yang D, Nieto J, Siddiqui A. et al. Lumen-apposing covered self-expandable metal stents for short benign gastrointestinal strictures: a multicenter study. Endoscopy 2017; 49: 327-333
• 7 Irani S, Jalaj S, Ross A. et al. Use of a lumen-apposing metal stent to treat GI strictures (with videos). Gastrointest Endosc 2016; DOI: 10.1016/j.gie.2016.08.028.
• 8 Majumder S, Buttar NS, Gostout C. et al. Lumen-apposing covered self-expanding metal stent for management of benign gastrointestinal strictures. Endosc Int Open 2016; 4: E96-E101