ELEMENT TRIAL: study protocol for a randomized controlled trial on endoscopic ultrasound-guided biliary drainage of first intent with a lumen-apposing metal stent vs. endoscopic retrograde cholangiopancreatography in the management of malignant distal biliary obstruction

Background & aims: Endoscopic ultrasound guided-biliary drainage (EUS-BD) is a promising alternative to endoscopic retrograde cholangiopancreatography (ERCP); however, its growth has been limited by a lack of multicenter randomized controlled trials (RCT) and dedicated devices. A dedicated EUS-BD lumen- apposing metal stent (LAMS) has recently been developed with the potential to greatly facilitate the technique and safety of the procedure. We aim to compare a first intent approach with EUS-guided choledochoduodenostomy with a dedicated biliary LAMS vs. standard ERCP in the management of malignant distal biliary obstruction. Methods: The ELEMENT trial is a multicenter single-blinded RCT involving 130 patients in nine Canadian centers. Patients with unresectable, locally advanced, or borderline resectable malignant distal biliary obstruction meeting the inclusion and exclusion criteria will be randomized to EUS-choledochoduodenostomy using a LAMS or ERCP with traditional metal stent insertion in a 1:1 proportion in blocks of four. Patients with hilar obstruction, resectable cancer, or benign disease are excluded. The primary endpoint is the rate of stent dysfunction needing re- intervention. Secondary outcomes include technical and clinical success, interruptions in chemotherapy, rate of surgical resection, time to stent dysfunction, and adverse events. Discussion: The ELEMENT trial is designed to assess whether EUS-guided choledochoduodenostomy using a dedicated LAMS is superior to conventional ERCP as a first- line endoscopic drainage approach in malignant distal biliary obstruction, which is an important and timely question that has not been addressed using an RCT study design.