Fully covered versus partially covered self-expandable metal stents for palliation of distal malignant biliary obstruction: a systematic review and meta-analysis

Self-expandable metal stents (SEMS) are standardly used for distal malignant biliary obstruction (dMBO). Whilst data suggest that Covered versus Uncovered SEMS increase Time to Recurrent Biliary Obstruction (TRBO), no data is available for Fully-Covered (FC) versus Partially-Covered (PC) design.Pubmed, Scopus and Cochrane databases were screened up to January-2023 for studies concerning dMBO treated by FC or PC-SEMS and describing Adverse Events (AEs), Recurrences or TRBO for specific design subpopulations. Pooled proportions or means [95% confidence interval] were calculated using a random-effects model. Several sub-analyses were pre-planned, including one restricted to prospective studies and unresectable diseases. Heterogeneity and Publication bias were explored. Standardized differences (d-values) were calculated between groups.From 1290 records, 62 studies (3327 FC-SEMS, 2322 PC-SEMS) were included. FC versus PC-SEMS showed negligible differences in the rate of total AEs (12% vs. 9.9%) and all specific AEs, including cholecystitis (2.5% vs. 2.6%). In sub-analysis restricted to prospective studies and unresectable diseases, rate of RBO was comparable between FC-SEMS (27.3% [23.7-31.2], I2=35.34%) versus PC-SEMS (25.3% [20.2-30.7], I2=85.09%), despite small differences (0.186-d-values-0.216) in the rate of ingrowth (0.5% vs 2.9%) favoring FC-SEMS and migration (9.8% vs 4.3%) favoring PC-SEMS. TRBO was shorter for FC-SEMS (238 [191-286] days, I2=63.1%) versus PC-SEMS (369 [290-449] days, I2=71.9%; d-value=0.116).Despite considerable heterogeneity and small standardized differences, PC-SEMS consistently exhibited longer TRBO than FC-SEMS across analyses, without any other differences in AEs rates, potentially proposing PC-SEMS as standard comparator and TRBO as primary outcome for future randomized studies on dMBO (CRD42023393965).