WONDER-02 Trial: Plastic Stent vs. Lumen-apposing Metal Stent for Pancreatic Pseudocysts

WONDER-02: Plastic Stent vs. Lumen-apposing Metal Stent for Endoscopic Ultrasound-guided Drainage of Pancreatic Pseudocysts-a Multicentre Randomised Non-inferiority Trial

Endoscopic ultrasound (EUS)-guided transluminal drainage has become a first-line treatment modality for symptomatic pancreatic pseudocysts. Despite the increasing popularity of lumen-apposing metal stents (LAMSs), the use of a LAMS is limited by its high costs and specific adverse events compared to plastic stent placement. To date, there has been a paucity of data on the appropriate stent type in this setting. This trial aims to assess the non-inferiority of plastic stents to a LAMS for the initial EUS-guided drainage of pseudocysts.

Pancreatic fluid collections (PFCs) develop as local complications of acute pancreatitis after four weeks of the disease onset. Pancreatic pseudocysts are a type of PFC, which is characterised by encapsulated non-necrotic contents. Pseudocysts occasionally become symptomatic (e.g., infection, GI symptoms), and given the high morbidity and mortality, it is mandatory to manage symptomatic pseudocysts appropriately to improve clinical outcomes of patients with acute pancreatitis overall. EUS-guided transluminal drainage has become a first-choice treatment option for symptomatic PFCs. In the setting of EUS-guided treatment of walled-off necrosis (WON, the other type of PFC), the potential benefits of LAMSs have been reported. Compared to plastic stents, LAMSs can serve as a transluminal port and thereby, facilitate the treatment of WON that often requires a long treatment duration with repeated interventions including direct endoscopic necrosectomy. With the increasing popularity and availability of LAMSs in interventional EUS overall, several retrospective studies have reported the feasibility of LAMS use for EUS-guided drainage of pancreatic pseudocysts.

While a LAMS may enhance the drainage efficiency of pseudocysts due to its large calibre, the benefits of this stent may be mitigated in pseudocysts that, by definition, contain non-necrotic liquid contents and can be managed without necrosectomy. Indeed, several retrospective comparative studies failed to demonstrate the superiority of plastic stents to a LAMS. In addition, the use of a LAMS has been limited by higher costs compared to plastic stents and potential specific adverse events (e.g., bleeding, buried stent). Studies suggest that a prolonged duration of LAMS placement (approximately ≥ 4 weeks) may predispose the patients to an elevated risk of adverse events associated with LAMSs. Therefore, patients requiring long-term drainage (e.g., cases with disconnected pancreatic duct syndrome) should be subjected to a reintervention in which a LAMS is replaced by a plastic stent. However, the technical success rate of the replacement has not been high. Given these lines of evidence, the investigators hypothesised that plastic stents might be non-inferior to a LAMS in terms of the potential of resolving a pseudocyst and associated symptoms.

To test the hypothesis, the investigators have planned a multicentre randomised controlled trial (RCT) to examine the non-inferiority of plastic stents to a LAMS as the initial stent for EUS-guided drainage of pancreatic pseudocysts in terms of the achievement of clinical treatment success (the resolution of a pseudocyst). Given the lower costs of plastic stents compared to a LAMS, the results would help not only establish a new treatment paradigm for pancreatic pseudocysts but also improve the cost-effectiveness of the resource-intensive treatment.

Inclusion Criteria:

• Patients with pancreatic pseudocyst(s) defined by the revised Atlanta classification
• The longest diameter of a targeted pseudocyst ≥ 5 cm
• Patients requiring drainage for symptoms associated with a pseudocyst (e.g., infection, gastrointestinal symptoms including abdominal pain, or jaundice)
• Patients aged 18 years or older
• Written informed consent obtained from patients or their representatives

Exclusion Criteria:

• A pseudocyst that is inaccessible via the EUS-guided approach
• A plastic or lumen-apposing metal stent in situ
• Coagulopathy (e.g., platelet count < 50,000/mm3 or prothrombin time international normalised ratio [PT-INR] >1.5)
• Users of antithrombotic agents that cannot be discontinued according to the Japan Gastroenterological Endoscopy Society [JGES] guidelines
• Patients who do not tolerate endoscopic procedures
• Pregnant women