12-mm Partial Covered Versus Bare Self-Expandable Metallic Stents for Malignant Distal Biliary Obstruction: A Prospective, Randomized Clinical Study

Malignant distal biliary obstruction is commonly caused by pancreatic cancer, cholangiocarcinoma, gallbladder cancer, or metastatic malignancy. In patients with unresectable disease, biliary drainage with a self-expandable metallic stent is widely used as palliative treatment. Bare metallic stents have the advantage of firm fixation, but tumor ingrowth can lead to recurrent biliary obstruction. Covered metallic stents may reduce tumor ingrowth, but concerns remain regarding stent migration and other procedure-related complications. Although 10-mm stents have been studied previously, evidence remains limited regarding the comparative effectiveness and safety of 12-mm partially covered versus bare self-expandable metallic stents.

This study is a prospective, single-center, randomized clinical trial designed to compare a 12-mm partially covered self-expandable metallic stent with a 12-mm bare self-expandable metallic stent in patients with unresectable malignant distal biliary obstruction. Adult patients who have already undergone percutaneous transhepatic biliary drainage (PTBD) according to the institutional clinical protocol and are scheduled for metallic stent placement through the existing PTBD tract will be screened for eligibility. After written informed consent is obtained, eligible participants will be randomly assigned in a 1:1 ratio to receive either a 12-mm partially covered self-expandable metallic stent or a 12-mm bare self-expandable metallic stent.

All procedures will be performed through a percutaneous transhepatic approach using the existing PTBD tract. After assessment of the biliary stricture, an appropriately sized 12-mm metallic stent will be placed. Participants will be followed for 12 months after stent placement, with follow-up assessments at 3, 6, and 12 months. The primary outcome is the cumulative incidence of recurrent biliary obstruction within 12 months after the procedure. Secondary outcomes include time to recurrent biliary obstruction, overall recurrent biliary obstruction rate, causes of recurrent biliary obstruction, reintervention, overall survival, and procedure-related complications such as pancreatitis, cholecystitis, bleeding, perforation, and cholangitis. The results of this study are expected to provide evidence to guide selection of the most appropriate 12-mm metallic stent in patients with unresectable malignant distal biliary obstruction.