Uncovered Self-Expandable Metallic Stent with an Ultra-Thin Delivery Sheath in Unresectable Malignant Hilar Biliary Obstruction: A Multicenter Prospective Observational Study

Background: Although various self-expandable metallic stents (SEMSs) for malignant hilar biliary obstruction (MHBO) have been introduced, the optimal SEMS for MHBO has not yet been established. Purpose: This study aimed to evaluate outcomes of the transpapillary placement of an uncovered laser-cut SEMS with an ultra-thin delivery sheath (YABUSAME) for MHBO. Methods: This multicenter, prospective study was conducted in 11 hospitals for 10 months (from March 2022 to December 2022). The primary outcome was the stent patency rate at 6 months. Key secondary outcomes were the technical success rate, clinical success rate, time to recurrent biliary obstruction (RBO), overall survival (OS), and adverse events. Results: Of 45 enrolled patients, 43 patients underwent biliary drainage, including 42 patients who underwent YABUSAME placement; 66.7% of patients received chemotherapy, and 60% had previously undergone biliary drainage. Drainage methods were partial stent-in-stent, side-by-side, and unilateral in 65.1%, 7.0%, and 27.9% of patients, respectively. Technical and clinical success rates were 93.2% (41/45) and 79.1% (34/45), respectively. The incidence rate of early postprocedural adverse events was 2.2%. The stent patency rate at 6 months was 55.3%. The median time to RBO was 231 days. The median OS was 125 days. Conclusion: This study showed that the primary outcome, the 6-month stent patency rate, exceeded the expected rate of 55%, which indicates the efficacy of YABUSAME placement for MHBO.