Feasibility of a Fully Covered Self-Expandable Metal Stent with a Central Waist and a Long Removal String for Management of Malignant Distal Biliary Obstruction: A Multicenter Prospective Pilot Study.

Background/Objectives: A fully covered self-expandable metal stent (FCSEMS) with a central waist and long retrieval string has recently been introduced for benign biliary strictures; however, its role in malignant biliary obstruction (MBO) remains unclear. This prospective, multicenter study evaluated the feasibility of palliation for unresectable distal MBO. Methods: Between April 2022 and March 2023, patients with extrahepatic MBO were enrolled across six tertiary referral centers. The FCSEMS was a silicone-covered, cross-wired nitinol stent with an anti-migration central waist 2 mm narrower than both ends, three radiopaque markers, and a 10 cm retrieval string. Stent-related outcomes and adverse events were analyzed. Results: Both technical and clinical success rates were 100% (46/46). The median stent patency and survival times were 251 and 360 days, respectively. Stent dysfunction occurred in 18 patients (39.1%), including 10 with migration and 8 with occlusion. Stent migration was observed exclusively in the transpapillary stenting group and showed no significant association with stricture length, stent-bending angle, or the ratio of stent lengths above and below the maximal bending point. All the occluded stents were successfully removed. Early non-recurrent biliary obstruction (RBO) adverse events occurred in five patients (three with pancreatitis, one with bleeding, one with cholecystitis), whereas late non-RBO events were reported in three patients (two with cholecystitis, one with cholangitis). Conclusions: An FCSEMS with a central waist and retrieval string is feasible for the palliation of unresectable distal MBO. Optimization of the mechanical properties is warranted to minimize migration.