Interpreting studies comparing lumen-apposing metal stents and plastic stents for walled-off necrosis: wisdom is the need of the hour

Lumen-apposing metal stents (LAMSs) are being increasingly used for the drainage of walled-off necrosis (WON). It was postulated that their placement, compared with plastic stents, is technically easier, decreases the need for necrosectomy, lowers adverse events, enables faster disease resolution, and is potentially more cost effective. However, with the exception of shorter procedural duration, other perceived advantages have not been borne out in randomized trials [1].

In this issue of Endoscopy, Moon et al. from South Korea compare the performance of a 16-mm novel electrocautery-enhanced LAMS (Niti-S HOT SPAXUS stent; Taewoong Medical, Goyang, South Korea) with that of 7-Fr plastic stents [2]. The study cohort comprised 46 patients with infected WON and the main outcome measure was number of necrosectomy procedures required to achieve clinical success. As observed in prior randomized trials, there was no difference in the primary outcome between study cohorts [3] [4] [5]. However, while there was no difference in clinical success, which was defined as partial or complete resolution of WON in conjunction with symptom resolution at 4 weeks, there was significant difference in favor of LAMS at 8 weeks.

“...while there was no difference in clinical success, which was defined as partial or complete resolution of WON in conjunction with symptom resolution at 4 weeks, there was significant difference in favor of LAMS at 8 weeks..., but there are several aspects worth contemplating while reviewing the findings of the present study.”

There are several aspects worth contemplating while reviewing the findings of the present study. First, while a 16-mm-diameter endoprosthesis was chosen for the LAMS cohort, in the plastic stent cohort, the transmural tract was accessed with a 6-Fr cystotome and dilated to only 4–6 mm before one or two 7-Fr endoprostheses were placed. The standard of care when treating pancreatic fluid collections using plastic stents is to perform 12–15-mm transmural tract dilation and place a minimum of 2–3 stents. In a recent report that compared outcomes between LAMS and plastic stents in 303 patients with pancreatic fluid collections, it was reported that placement of two 7-Fr plastic stents (after transmural tract dilation to 12–15 mm) was associated with a higher proportion of organ failure and systemic inflammatory response at 48 hours, particularly in patients with greater than 33% necrosis [6].

Second, while the median degree of necrosis in the present study was reported to be 70% or more in both groups, disconnected pancreatic duct syndrome (DPDS) was observed in less than 5% of the study cohort. In a prior randomized trial comparing endoscopy and minimally invasive surgery for treatment of necrotizing pancreatitis, it was observed that a median of 40% necrosis was associated with DPDS in more than 80% of patients [7]. Similarly, DPDS was observed in 41.9%–51.8% of patients who received LAMS or plastic stents in two recent randomized trials [3] [5]. It is important to note that the degree of necrosis was still significantly less in both those clinical trials compared with the present study.

Third, in the present study, endoscopic necrosectomy was performed in 13.0% of plastic stent and 21.7% of LAMS cohorts compared with a pooled estimate mean of 38.5% for LAMS (95%CI 10.5–71.6) and 41.2% (95%CI 22.0–61.9) for plastic stent cohorts in the meta-analysis of three randomized trials [1].

Fourth, clinical success in two prior randomized trials was defined as complete resolution of WON in conjunction with symptom relief, whereas in the present study it was defined as reduction in size of the necrotic collection to more than 50% at 4 weeks accompanied by symptom relief.

Finally, outcomes in WON can be ascertained reliably only when the follow-up duration is adequate – usually 6 months after index hospital discharge. In the present study, clinical success was ascertained at 4 weeks post-procedure and final follow-up was conducted at 3 months. Cross-sectional imaging to ascertain the complete resolution of the disease process was not performed. While it may be reasonable to assume that both stents performed equally well in the present study, the probability that LAMS yielded higher clinical success at 8 weeks cannot be justified due to the serious, significant, limitations outlined above and the very small sample size of 46 patients.

While randomized trials may be difficult to execute, the study design should still be rigorous, sample size adequately powered, and follow-up duration reasonably long to capture all relevant clinical end points. Otherwise, the study findings become difficult to interpret and it is left to the wisdom of the readers to search for those hidden pearls that may or may not meaningfully impact their clinical practice.

Publication History

Article published online:
07 August 2024

• References

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