Plastic Stent-Based Management Versus Metal Stent Exposure for Lifelong Biliary Drainage in Unresectable Malignant Hilar Biliary Obstruction.

Background and study aims Self-expandable metal stents (SEMS) are widely used for malignant hilar biliary obstruction (MHBO), but whether they improve long-term drainage over plastic stents (PS) is uncertain. As chemotherapy prolongs survival, biliary drainage must be sustained across the remaining disease course. We compared failure of intended lifelong biliary drainage (LDF) between PS-based management and SEMS exposure using a causal inference framework. Patients and methods We retrospectively studied 608 consecutive patients who underwent initial endoscopic drainage for unresectable MHBO at 22 Japanese tertiary centers between January 2020 and March 2024. SEMS use was modeled as a time-varying, irreversible exposure. A marginal structural model with stabilized inverse probability of treatment and censoring weights estimated the adjusted odds ratio (OR) for LDF, defined as the point at which drainage could no longer be maintained by any endoscopic, EUS-guided, or percutaneous approach. Results Over a median follow-up of 184 days, 130 patients (21.4%) had LDF and 384 (63.2%) died. SEMS exposure was associated with higher odds of LDF (adjusted OR, 1.87; 95% CI, 1.28-2.73; P = 0.001), consistent across sensitivity analyses (OR range, 1.75-2.53). The association strengthened from 1.79 at 90 days to 2.93 at 450 days. Cumulative costs were higher in an exploratory analysis. Conclusions SEMS exposure was associated with higher odds of LDF and higher costs than PS-based management. These findings are hypothesis-generating, and prospective studies are needed to determine whether routine first-line SEMS use should be reconsidered when biliary drainage is intended to last across the remaining disease course.