Self-expandable metal stents (SEMSs) are used to relieve malignant biliary obstructions. We aimed to compare stent patency, the adverse events rate, and overall survival of covered versus uncovered self-conformable metal stents in patients with primary malignant extrahepatic biliary strictures, not eligible for surgery.

This is a multicenter randomized trial analyzing 158 patients with inoperable distal malignant biliary obstruction conducted in 5 Italian referral centers between December 2014 and October 2016. Seventy-eight patients were randomized to receive a fully covered SEMS (FCSEMS), and 80 patients received uncovered SEMSs (USEMSs). Data from 148 (72 FCSEMSs and 76 USEMSs) of 158 patients were analyzed.

Median time of stent patency was lower for FCSEMSs (240 days vs 541 days for USEMSs; P = .031). Adverse events occurred with 19 FCSEMSs (26.4%) and 10 USEMSs (13.2%); P = .061. The main causes of FCSEMS dysfunction were migration (7% vs 0% in the USEMS group) and early occlusion mainly because of sludge or overgrowth; late stent occlusion because of tumor ingrowth occurred in 13.2% of patients in the USEMS group. There were no significant differences either in levels of conjugated bilirubin improvement or in overall survival between the FCSEMS and USEMS groups. Median survival was 134 days in the FCSEMS group and 112 days in the USEMS group (P = .23).

The number of stent-related adverse events was higher, although not significantly, among patients in the FCSEMS group. FCSEMSs had a significantly higher rate of migration than USEMSs, and stent occlusion occurred earlier. A significant difference in the patency rate was observed in favor of the USEMS group. (Clinical trial registration number: NCT02102984.)