Safety and efficacy of lumen-apposing metal stents for endoscopic ultrasound-guided drainage of pancreatic fluid collections: a systematic review and meta-analysis

Introduction

Pancreatic fluid collections (PFCs) are a well-known complication of acute pancreatitis. Based on the revised Atlanta classification, PFCs can be classified as acute peripancreatic fluid collections, pancreatic pseudocysts, acute necrotic collections, and walled-off necrosis (WON). The time of onset (more than or fewer than 4 weeks) and the presence or absence of necrosis determine the type of PFC [1]. Given that percutaneous drainage has a higher risk of formation of a pancreaticocutaneous fistula, and the surgical approach to drainage and debridement of PFCs has higher morbidity, the endoscopic approach is preferred as the first-line intervention for the management of PFCs [2] [3]. Plastic stents, self-expandable metal stents (SEMSs), and lumen-apposing metal stents (LAMSs) – a type of SEMS – can be used for endoscopic ultrasound (EUS)-guided drainage of pancreatic collections [4] [5]. Although studies have shown mixed results regarding the superiority of LAMSs over plastic stents, LAMSs appear to be the preferred type of stent in routine clinical practice for the endoscopic management of PFCs [6] [7].

There are several types of commercially available LAMS for EUS-guided drainage of PFCs ([Fig. 1]). The three most widely used and studied stents from across the globe are the Axios, Nagi, and Spaxus stents. Many studies have demonstrated the safety and efficacy of all three of these devices in the management of PFCs [8] [9] [10] [11] [12] [13]. The Nagi stent (Niti-s NAGI; Taewoong Medical, Gyeonggi-do, Seoul, South Korea) is a biflanged metal stent designed to prevent spontaneous migration. It is made of nitinol with a silicone coating. The Spaxus stent (Niti-S SPAXUS; Taewoong Medical Co., Ltd., Ilsan, South Korea) is a LAMS made of nitinol and a silicone membrane with a conventional stent delivery system. It has large flanges at both ends to provide anchorage. Once deployed, both flanges fold back to hold the two gastrointestinal lumens in apposition. The Axios stent (Boston Scientific, Marlborough, Massachusetts, USA) is another type of LAMS that currently is the only commercially available LAMS in the USA. It is barbell-shaped, made of nitinol, and is fully covered. It comes with a catheter-based delivery system.

Fig. 1 Endoscopic view of a lumen-apposing metal stent successfully placed with endoscopic ultrasound guidance to drain a pancreatic fluid collection.

To date, only a few studies have compared the different types of LAMS [14] [15] [16] [17], with robust large-scale data comparing these three LAMSs lacking. Therefore, we aimed to perform a systematic review and meta-analysis comparing the safety and efficacy of the Spaxus, Nagi, and Axios stents for EUS-guided drainage of PFCs.

Methods

Search strategy

A comprehensive search of databases, including EMBASE, PubMed, and SCOPUS, was conducted from inception to 30 January 2024. An expert medical librarian helped perform the literature search with the study authors’ input. Keywords used in the search included, but were not limited to, the following terms: “EUS,” “LAMS,” “AXIOS,” “SPAXUS,” “NAGI,” “PFC,” “pseudocyst,” and “WON.” We used the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines for this meta-analysis (Fig. 1s, see online-only Supplementary material). We restricted our search to studies published in peer-reviewed journals or presented as abstracts at national society meetings. Two authors (V.C.S.K. and S.S.) independently screened the studies for eligibility. Any discrepancy about including studies was resolved by a co-author (B.P.M.).

Study selection

The inclusion criteria were: (i) patients undergoing EUS-guided drainage of a PFC; (ii) age >18 years; (iii) use of a LAMS; (iv) data available on the safety and efficacy of the stent. Case series of less than 10 patients and case reports were excluded.

Data abstraction and quality assessment

A data extraction sheet was created, and the study characteristics, data on intended outcomes, and patient characteristics were collected. S.S. and V.C.S.K. independently extracted the data. All the data were reviewed by a co-author (H.M.A.K.) for potential discrepancies and were resolved. Multiple attempts or LAMS placements in individual patients were not included.

The quality of the included studies was determined using the Newcastle–Ottawa scale. The scale consists of six questions, with each receiving 0, 1, or 2 points depending on how well the study has met the criteria. Two authors (V.C.S.K. and S.S.) independently assessed the quality of the studies. The senior author (D.G.A.) reviewed the final quality assessment table and resolved any discrepancies.

Outcomes assessed

The outcomes of interest were: technical success; clinical success; adverse events (AEs) including migration, bleeding, perforation, and infection; and the need for endoscopic necrosectomy. We performed subgroup analysis according to the severity of bleeding (based on the American Society for Gastrointestinal Endoscopy [ASGE] lexicon) and the type of PFC wherever applicable.

Statistical analysis

Pooled proportions with 95%CIs were calculated using a random-effects model (DerSimonian–Laird's method). We assessed heterogeneity between study-specific estimates by I ² statistics. In this, values of <30%, 30%–60%, 61%–75%, and >75% are suggestive of low, moderate, substantial, and considerable heterogeneity, respectively. Publication bias was ascertained qualitatively by visual inspection of the funnel plot and quantitatively by the Egger’s test. All analyses were performed using Comprehensive Meta-Analysis (CMA) software, version 4 (BioStat, Englewood, New Jersey, USA) and MedCalc Statistical Software version 19.1.3 (MedCalc Software bv, Ostend, Belgium; https://www.medcalc.org/; 2019).

Results

Included studies

Of the 1031 studies found on the initial search, 37 eligible studies were ultimately selected and included in the final analysis, with a total of 3074 patients ([Table 1]; Table 1s). Of these, 29 studies were retrospective, seven were prospective, and one was a randomized trial. The number of studies for the different stents were 26 for the Axios stent [10] [11] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26] [27] [28] [29] [30] [31] [32] [33] [34] [35] [36] [37], nine for the Nagi stent [8] [13] [14] [15] [17] [38] [39] [40] [41], and six for the Spaxus stent [12] [16] [42] [43] [44] [45].

Table 1 Baseline characteristics of the studies on the Nagi and Spaxus stents.

Study	Type	Indication	Number of patients	Mean age, years	Male, %
PFC, pancreatic fluid collection; WON, walled-off necrosis.
Nagi
Ang 2016 [8]	Retrospective	PFCs	16	50	43.8
Bekkali 2017 [14]	Retrospective	WON	40	63	67.5
Chandran 2015 [38]	Retrospective	Pancreatic collections	47	51	68.1
Coluccio 2024 [15]	Retrospective	Pancreatic collections	84	63	61
Dhir 2015 [13]	Prospective	Pseudocyst	47	38	59.6
Lakhtakia 2017 [39]	Retrospective	WON	205	34.8	88.3
Mukai 2014 [40]	Retrospective	PFCs	21	57.3	81
Petrone 2018 [41]	Retrospective	PFCs	67	58.8	68.7
Siddiqui 2021 [17]	Retrospective	WON	205	34.8	88.3
Spaxus
Mangiavillano 2024 [16]	Retrospective	PFCs	132	54	69.6
Oh 2022 [42]	Retrospective	PFCs	47	59.8	53.2
Paduano 2023 [43]	Retrospective	PFCs	162	54	70
Shin 2018 [44]	Retrospective	PFCs	10	55.8	80
Song 2019 [12]	Prospective	Pancreatic pseudocysts	34	51.7	76.5
Teoh 2020 [46]	Prospective	PFCs	59	44.9	81.4

Meta-analysis outcomes

Axios stent

A total of 1898 patients (mean age 56 years; 63% men) were included. The pooled outcomes for PFCs were as follows: technical success 97.7% (95%CI 96.4%–98.8%), clinical success 90.9% (95%CI 88.7%–92.8%), total AEs 20.4% (95%CI 16.6%–24.6%), migration 4.2% (95%CI 2.9%–5.7%), overall bleeding 7.0% (95%CI 4.9%–9.5%), mild bleeding 0.8% (95%CI 0.3%–1.6%), moderate bleeding 1.8% (95%CI 0.8%–3.2%), severe bleeding 2.5% (95%CI 1.4%–4.0%), perforation 1.4% (95%CI 0.7%–2.5%), and infection 6.9% (95%CI 4.7%–9.5%) ([Fig. 2]; [Table 2]). Endoscopic necrosectomy was performed in 54.5% of patients (95%CI 38.9%–69.7%).

Fig. 2 Pooled adverse events for the Axios stent are shown as a forest plot, including the study proportions and weight.

Table 2 Pooled outcomes for the three different stent types and different types of collection.

Outcome	Axios			Nagi			Spaxus1
	PFC2	Pseudocyst3	WON	PFC2	Pseudocyst3	WON	PFC2
PFC, pancreatic fluid collection; WON, walled-off necrosis. 1 Owing to the limited number of studies providing relevant data, subgroup analysis of the Spaxus stent based on PFC type could not be assessed. 2 PFC is the overall group including pseudocysts, WON, and PFC of unspecified type. 3 No result is given where there were insufficient studies available for pooled analysis. 4 I 2 statistics could not be generated.
Technical success (95%CI), %	97.7 (96.4–98.8); I 2 = 62%	97.4 (94.4–99.3); I 2 = 0%	98.4 (96.9–99.4); I 2 = 39%	96.9 (94.6–98.5); I 2 = 49%	94.0 (86.6–98.6); I 2 = 36%	97.8 (94.6–99.6); I 2 = 61%	98.2 (94.4–99.9); I 2 = 76%
Clinical success (95%CI), %	90.9 (88.7–92.8); I 2 = 46%	95.4 (90.9–98.4); I 2 = 3%	89.8 (85.3–93.6); I 2 = 66%	88.5 (79.9–95.0); I 2 = 89%	88.7 (81.1–94.6); I 2 = 37%	82.0 (65.1–94.2); I 2 = 93%	93.5 (91.0–95.6); I 2 = 0%
Adverse events (95%CI), %	20.4 (16.6–24.6); I 2 = 76%	14.1 (7.3–22.8); I 2 = 44%	23.6 (17.5–30.4); I 2 = 75%	17.1 (8.3–28.3); I 2 = 92%	17.6 (3.7–38.8); I 2 = 87%	20.2 (8.3–35.7); I 2 = 91%	7.6 (3.6–13.0); I 2 = 66%
Migration (95%CI), %	4.2 (2.9–5.7); I 2 = 48%	7.8 (3.5–13.6); I 2 = 24%	3.4 (1.8–5.6); I 2 = 46%	7.8 (4.1–12.4); I 2 = 74%	3.3 (0.3–9.4); I2 = 57%	9.0 (6.6–11.7); I2 = 0%	0.9 (0.1–2.8); I 2 = 52%
Bleeding (95%CI), %	7.0 (4.9–9.5); I 2 = 69%	1.0 (0.1–3.2); I 2 = 0%	7.1 (3.8–11.2); I 2 = 64%	4.4 (2.2–7.4); I 2 = 55%	–	2.1 (0.9–3.7); I 2 = 0%	1.8 (0.8–3.3); I 2 = 0%
Mild bleeding (95%CI), %	0.8 (0.3–1.6); I 2 = 26%	0.5 (0.0–2.6); I 2 = 0%	0.4 (0.0–1.3); I 2 = 0%	0.8 (0.1–2.1); I 2 = 29%	–	0.8 (0.0–4.0); I 2 = 81%	0.3 (0.0–1.0); I 2 = 0%
Moderate bleeding (95%CI), %	1.8 (0.8–3.2); I 2 = 57%	0.5 (0.0–2.6); I 2 = 0%	1.2 (0.3–2.9); I 2 = 24%	2.0 (0.4–4.6); I 2 = 56%	–	0.7 (0.1–1.8)4	0.6 (0.1–1.6); I 2 = 12%
Severe bleeding (95%CI), %	2.5 (1.4–4.0); I 2 = 50%	0.5 (0.0–2.6); I 2 = 0%	3.0 (1.0–6.1); I 2 = 58%	1.0 (0.3–2.1); I 2 = 0%	–	0.7 (0.1–1.8)4	1.5 (0.6–2.9); I 2 = 0%
Perforation (95%CI), %	1.4 (0.7–2.5); I 2 = 39%	1.3 (0.0–5.0); I 2 = 27%	3.1 (1.3–5.6); I 2 = 14%	1.5 (0.7–2.7); I 2 = 0%	–	1.2 (0.4–2.5)4	0.2 (0.0–1.0); I 2 = 0%
Infection (95%CI), %	6.9 (4.7–9.5); I 2 = 63%	8.5 (0.8–23.2); I 2 = 77%	10.1 (5.5–15.9); I 2 = 69%	6.1 (4.1–8.5); I 2 = 0%	7.8 (2.8–14.9); I 2 = 15%	7.8 (4.6–11.8); I 2 = 0%	9.6 (4.2–16.8); I 2 = 0%
Endoscopic necrosectomy (95%CI), %	54.5 (38.9–69.7); I 2 = 97%	–	70.7 (54.1–84.9); I 2 = 94%	16.0 (11.4–21.3); I 2 = 58%	–	15.0 (8.2–23.3); I 2 = 74%	19.9 (6.6–38.1); I 2 = 94%

Pseudocyst The pooled outcomes for Axios stent use in pseudocysts were: technical success 97.4% (95%CI 94.4%–99.3%), clinical success 95.4% (95%CI 90.9%–98.4%), total AEs 14.1% (95%CI 7.3%–22.8%), migration 7.8% (95%CI 3.5%–13.6%), overall bleeding 1.0% (95%CI 0.1%–3.2%), mild bleeding 0.5% (95%CI 0.0%–2.6%), moderate bleeding 0.5% (95%CI 0.0%–2.6%), severe bleeding 0.5% (95%CI 0.0%–2.6%), perforation 1.3% (95%CI 0.0%–5.0%), and infection 8.5% (95%CI 0.8%–23.2%). The pooled endoscopic necrosectomy rate could not be calculated owing to lack of sufficient data.

WON The pooled outcomes were: technical success 98.4% (95%CI 96.9%–99.4%), clinical success 89.8% (95%CI 85.3%–93.6%), total AEs 23.6% (95%CI 17.5%–30.4%), migration 3.4% (95%CI 1.8%–5.6%), overall bleeding 7.1% (95%CI 3.8%–11.2%), mild bleeding 0.4% (95%CI 0.0%–1.3%), moderate bleeding 1.2% (95%CI 0.3%–2.9%), severe bleeding 3% (95%CI 1.0%–6.1%), perforation 3.1% (95%CI 1.3%–5.6%), infection 10.1% (95%CI 5.5%–15.9%), and endoscopic necrosectomy 70.7% (95%CI 54.1%–84.9%).

Nagi stent

A total of 732 patients (mean age 50 years; 70% men) were included. The pooled outcomes for PFCs were: technical success 96.9% (95%CI 94.6%–98.5%), clinical success 88.5% (95%CI 79.9%–95.0%), total AEs 17.1% (95%CI 8.3%–28.3%), migration 7.8% (95%CI 4.1%–12.4%), overall bleeding 4.4% (95%CI 2.2%–7.4%), mild bleeding 0.8% (95%CI 0.1%–2.1%), moderate bleeding 2.0% (95%CI 0.4%–4.6%), severe bleeding 1.0% (95%CI 0.3%–2.1%), perforation 1.5% (95%CI 0.7%–2.7%), and infection 6.1% (95%CI 4.1%–8.5%) ([Fig. 3]; [Table 2]). Endoscopic necrosectomy was performed in 16.0% of patients (95%CI 11.4%–21.3%).

Fig. 3 Pooled adverse events for the Nagi stent are shown as a forest plot, including the study proportions and weight.

Pseudocyst The pooled outcomes for Nagi stent use in pseudocysts were: technical success 94.0% (95%CI 86.6%–98.6%), clinical success 88.7% (95%CI 81.1%–94.6%), total AEs 17.6% (95%CI 3.7%–38.8%), migration 3.3% (95%CI 0.3%–9.4%), and infection 7.8% (95%CI 2.8%–14.9%). Sufficient data were not available in the studies for other pooled outcomes.

WON The pooled outcomes were: technical success 97.8% (95%CI 94.6%–99.6%), clinical success 82.0% (95%CI 65.1%–94.2%), total AEs 20.2% (95%CI 8.3%–35.7%), migration 9.0% (95%CI 6.6%–11.7%), overall bleeding 2.1% (95%CI 0.9%–3.7%), mild bleeding 0.8% (95%CI 0.0%–4.0%), moderate bleeding 0.7% (95%CI 0.1%–1.8%), severe bleeding 0.7% (95%CI 0.1%–1.8%), perforation 1.2% (95%CI 0.4%–2.5%), infection 7.8% (95%CI 4.6%–11.8%), and endoscopic necrosectomy 15.0% (95%CI 8.2%–23.3%).

Spaxus stent

A total of 444 patients (mean age 53 years; 72% men) were included. The pooled outcomes for PFCs were: technical success 98.2% (95%CI 94.4%–99.9%), clinical success 93.5% (95%CI 91.0%–95.6%), total AEs 7.6% (95%CI 3.6%–13.0%), migration 0.9% (95%CI 0.1%–2.8%), overall bleeding 1.8% (95%CI 0.8%–3.3%), mild bleeding 0.3% (95%CI 0.0%–1.0%), moderate bleeding 0.6% (95%CI 0.1%–1.6%), severe bleeding 1.5% (95%CI 0.6%–2.9%), perforation 0.2% (95%CI 0.0%–1.0%), and infection 9.6% (95%CI 4.2%–16.8%) ([Fig. 4]; [Table 2]). Endoscopic necrosectomy was performed in 19.9% of patients (95%CI 6.6%–38.1%). Subgroups based on the type of PFC could not be created as there were not sufficient studies available that provided the data.

Fig. 4 Pooled adverse events for the Spaxus stent are shown as a forest plot, including the study proportions and weight.

Sensitivity analysis

To assess the possible dominant effect of individual studies on the meta-analysis, we excluded one study at a time and analyzed its effect on the main summary estimate. We did not find any single study that significantly affected the outcomes of interest.

Heterogeneity

Based on the I ² analysis, substantial-to-considerable heterogeneity was found in some of the outcomes. [Table 2] shows the I ² values for PFCs and their subgroups according to the type of stents.

Publication bias

Quality assessment of the studies based on the Newcastle–Ottawa scale is summarized in Tables 2s–4s. The following had significant bias on Egger’s test: technical success, total AEs, and perforation (Axios); bleeding (Nagi); and total AEs and perforation (Spaxus). The funnel plots for each type of stent are shown in Fig. 2s.

Discussion

Our study demonstrated that the Axios, Spaxus, and Nagi stents had excellent pooled rates of technical success for EUS-guided drainage of PFCs. Although the pooled rates of clinical success were high among all three stents, the Spaxus stent had the highest clinical success compared with the others. Several studies that have evaluated the efficacy of all three stents individually for EUS-guided drainage of PFCs have shown good technical and clinical success [11] [13] [16]. Head-to-head studies comparing the Nagi and Axios stents showed that the technical and clinical success rates for EUS-guided PFC drainage were similar [14] [15] [17]. Similarly, a recent study by Mangiavillano et al. that included 132 patients in each group showed that the technical and clinical success rates were comparable between the Spaxus and Axios stents [16].

In our study, the pooled rates for total AEs, mainly contributed to by the WON subgroup, were highest with the Axios stent (20.4%), followed by the Nagi stent (17.1%), and lowest with the Spaxus stent (7.6%). We found that the pooled rates of bleeding were lowest with the Spaxus (1.8%) compared with the Axios (7.0%) and Nagi stents (4.4%). Compared with the Axios (4.2%) and Spaxus stents (0.9%), the Nagi (7.8%) had the highest rate of migration. Our findings appear to correlate with a previous head-to-head study comparing the Spaxus and Axios stents, which showed a significantly lower AE rate (3.0% vs. 9.8%; P = 0.04) and bleeding rate (1.5% vs. 7.5%; P = 0.04) with the Spaxus stent compared with the Axios [16]. The rate of migration was also observed to be lower; however, this was not statistically significant [16].

Initial studies performed using the so-called “Cold” Axios delivery system, which lacked an electrocautery-enhanced catheter tip, reported low rates of bleeding ranging between 0.02% and 0.6% [11] [47]; however, with the addition of an electrocautery-enhanced catheter tip, termed “Hot” Axios, the rate and number of total AEs, and the rate of bleeding were found to be significantly higher at 24.3% and 7.2%, respectively, in an international multicenter study [18]. The use of electrocautery-enhanced LAMSs is thought to play a role in the difference in AEs [46]. Given that the Spaxus and Nagi stents were initially used without electrocautery and have only recently incorporated an electrocautery tip for their “Hot” versions, the total AEs, including bleeding, might be under-represented with regards to the Spaxus and Nagi devices.

The strengths of this study include it being the first and only meta-analysis to compare outcomes for the endoscopic drainage of PFCs for all three commercially available LAMSs. Pooling patient data, with a large number of cases, provides additional power to the results compared with individual studies in each group. Most of the included studies were high quality studies, and there were no poor quality studies included in our meta-analysis. Given that certain LAMSs are currently unavailable in different regions of the world, it would be interesting to see the outcomes with US-based studies in the future, especially as it is reported that the Spaxus stent will be available soon.

Most of the limitations of this study are inherent to a meta-analysis. First, most of the studies were done at tertiary-level centers by expert gastroenterologists. Second, our analysis included studies that were retrospective in nature, potentially contributing to selection bias. Third, there was substantial-to-considerable heterogeneity seen in some of the outcomes, likely owing to the differences in baseline patient characteristics. Inter-user variability and local expertise with individual stents needs to be considered while interpreting the results of this study. Fourth, the use of coaxial stents could have likely impacted the overall outcomes. As the studies did not report outcomes with and without the coaxial stents, we could not analyze subgroups based on this. Fifth, the significance of the differences in the three stents could not be evaluated as this is an indirect comparison. Sixth, owing to the limited number of studies providing relevant data, certain outcomes, such as subgroup analysis of the Spaxus stents based on PFC type, could not be assessed. Additionally, outcomes such as secondary infection appear to be higher with the use of the Spaxus stent; however, the variable number of studies available in the three stent groups must be taken into account. Seventh, only a few studies provided data for bleeding according to severity grade, which likely explains the difference in overall bleeding and the sum of the mild, moderate, and severe bleeding percentages.

In conclusion, this systematic review and meta-analysis comparing the safety and efficacy of the Axios, Nagi, and Spaxus stents for EUS-guided drainage of PFCs shows good technical and clinical success with all three LAMSs The total AEs and rate of bleeding were highest with the Axios and lowest with the Spaxus stent. Stent migration was highest with the Nagi stent and lowest with the Spaxus. Future randomized trials and cost-effectiveness studies are needed to corroborate our findings.

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