Is bigger always better?

In the management of symptomatic walled-off necrosis (WON), the available minimally therapeutic interventions include surgical, percutaneous, and endoscopic drainage. Nowadays, the endoscopic approach is considered the first-line treatment for WON owing to various advantages over surgical or percutaneous approaches, and recent trials have shown that endoscopic drainage offers better clinical outcomes, with improvement in quality of life, shorter hospital stays, and lower costs [1].

Endoscopic transmural drainage (ETD) plus direct endoscopic necrosectomy (DEN) was first described in 1996 by Baron et al., and it represents a viable technique that is reasonably safe and effective when carried out in dedicated centers. The use of DEN should be reserved for patients with large amounts of necrosis who do not adequately respond to ETD using any type of stent (metal or plastic) combined with irrigation (endoscopic or via nasal catheters). DEN should be performed in centers that have experience in the management of pancreatic necrosis, and should be well supported by interventional radiologists, endoscopists, and surgeons [2].

With continuous technological advances and the appearance of new materials in the endoscopy field, doubts have arisen as to which devices are best to use. One clear example of this hesitation is in the choice of stent. To date, most published studies of ETD have involved plastic stents, with the number and diameter varying depending on the collection type and size. In the past, some reports have been published on the use of self-expandable covered metal stents as offering greater diameter. However, both types of stent are intended for bile drainage and are not designed for transmural drainage.

“LAMS are really replacing plastic stents but there is no quality scientific evidence to recommend LAMS as the standard in the management of WON, and the hypothetical superiority of LAMS needs to be demonstrated.”

Recently, lumen-apposing metal stents (LAMS) designed for the drainage of pancreatic collections have appeared, with demonstrated efficacy in recent meta-analyses and clinical practice updates that seem to favor them over plastic stents. The theoretical benefits of LAMS are the large diameter that improves WON drainage and enables less time-consuming interventions and a smaller number of endoscopic procedures to achieve DEN. Regarding safety, the risk of adverse events would theoretically be reduced using their specific stent design. However, LAMS are more expensive and their safety is controversial, with a significantly higher rate of adverse events such as bleeding and “buried stent syndrome” compared with plastic stents. The European Society of Gastrointestinal Endoscopy recommends retrieval of LAMS within 4 weeks in order to prevent these stent-related adverse events.

In this issue of Endoscopy, a study by Parsa et al. evaluates the use of a bigger LAMS in the management of symptomatic WON [3]. This was a retrospective comparative study at 22 centers, and the main aim was to compare the 15-mm and 20-mm LAMS in terms of technical success, clinical success, and adverse events. The authors conclude that the 20-mm LAMS offers a similar efficacy and safety profile to the 15-mm device, while requiring significantly fewer DEN sessions [3].

Despite the limitations of this study, it raises crucial questions relating to which stents are better at maintaining transmural access: Is metal superior to plastic? Is LAMS superior to plastic? Are LAMS safe? Is it useful to insert a plastic stent within a LAMS? What is the optimal timing for LAMS removal? And, related to Parsa et al., is bigger really better or is there an increase in adverse events?

It is reasonable to believe that larger-diameter metal stents (15 or 20 mm) provide greater output of necrotic material than plastic stents, while also allowing better endoscopic access for DEN if needed. But several concerns arise in the minds of endoscopists. For example, if the LAMS diameter is wider, along with the area of contact and LAMS-induced vessel erosion, is there increased risk of bleeding? Another concern relates to the greater risk of food reflux into the collection cavity if the stent diameter is wider. Following this concern, a novel LAMS with an antireflux valve to prevent infectious complications caused by food reflux was recently described [4]. Finally, what is the ideal WON to warrant a bigger stent (WON size, proportion of solid to liquid material)?

Returning to the basic question of which stent is best, LAMS are really displacing plastic stents. However, to date, there is no quality scientific evidence to recommend LAMS as the standard in the management of WON, and the hypothetical superiority of LAMS needs to be demonstrated. Against the recent opinion from international systematic reviews or meta-analyses (majority based on retrospective, registry-based, or noncomparative studies), the only randomized trial published to date did not exhibit superiority of LAMS over plastic stents [5]. This trial concluded that there were no significant differences in treatment outcomes between the stents, and the authors recommend follow-up imaging and LAMS removal at 3 weeks if collection is resolved, in order to minimize LAMS-related adverse events [5].

Similarly, data from a recent large international retrospective study confirmed that the use of LAMS had excellent technical and clinical success rates, but the rate of adverse events (24.3 %) was not negligible and should be carefully considered before using these stents for drainage of pancreatic fluid collections, and in particular for WON [6].

In order to avoid the risk of LAMS-related adverse events, many endoscopists place one or more plastic stents within LAMS to prevent occlusion by necrotic tissue, migration, and vessel erosion (creating a buffer between the stent and the vessel).

Well-designed prospective studies and randomized controlled trials in this field are needed to address all of these questions. To date, there are two comparative prospective studies of self-expandable LAMS-type metal stents versus plastic stents in the endoscopic treatment of WON, from China (NCT03027895) and Spain (NCT03100578) [7] [8]. Therefore, it is expected, and we are hopeful, that these studies and others will provide more information to clarify existing doubts about the efficacy and safety of LAMS.

Publication History

Article published online:
25 February 2020

• References

• 1 van Brunschot S, van Grinsven J, van Santvoort HC. et al. Endoscopic or surgical step-up approach for infected necrotising pancreatitis: a multicentre randomised trial. Lancet 2018; 391: 51-58
• 2 Baron TH, DiMaio CJ, Wang AY. et al. American Gastroenterological Association Clinical Practice Update: Management of pancreatic necrosis. Gastroenterology 2020; 158: 67-75
• 3 Parsa N, Nieto JM, Powers P. et al. Endoscopic ultrasound-guided drainage of pancreatic walled-off necrosis using 20-mm versus 15-mm lumen-apposing metal stents: an international, multicenter, case-matched study. Endoscopy 2020; 52: 211-219
• 4 Cho IR, Chung MJ, Jo JH. et al. A novel lumen-apposing metal stent with an anti-reflux valve for endoscopic ultrasound-guided drainage of pseudocysts and walled-off necrosis: a pilot study. PLoS One 2019; 14: e0221812
• 5 Bang JY, Navaneethan U, Hassan M. et al. Non superiority of lumen-apposing metal stents over plastic stents for drainage of walled off necrosis in a randomised trial. Gut 2019; 68: 1200-1209
• 6 Fugazza A, Sethi A, Trindade AJ. et al. International multicenter comprehensive analysis of adverse events associated with lumen-apposing metal stent placement for pancreatic fluid collection drainage. Gastrointest Endosc 2019; pii: S0016-5107(19)32471-X. doi: 10.1016/j.gie.2019.11.021
• 7 Zhu HY, Xie P, Song YX. et al. Lumen-apposing metal stents (LAMS) versus plastic stents for EUS-guided drainage of walled-off necrosis (WON) (LVPWON): study protocol for a multicenter randomized controlled trial. Trials 2018; 19: 549
• 8 Gornals JB, Perez-Miranda M, Vazquez-Sequeiros E. et al. Multicenter study of plastic vs. self-expanding metal stents in endoscopic ultrasound-guided drainage of walled-off pancreatic necrosis – PROMETHEUS: a randomized controlled trial protocol. Trials 2019; 20: 791