Evaluation of a 12-mm diameter covered self-expandable end bare metal stent for malignant biliary obstruction

Background and study aims Biliary metallic stents are used to drain unresectable malignant distal biliary obstructions. This study aimed to evaluate the efficacy of a novel 12-mm-diameter covered, self-expandable end bare metal stent (12-mm CSEEMS). Patients and methods We evaluated 99 patients with unresectable malignant distal biliary obstructions treated with covered biliary metallic stents. Of the 99 patients, 33 underwent 12-mm CSEEMS placement between June 2015 and April 2017 (12-mm-CSEEMS group) and 66 underwent 10-mm fully-covered self-expandable metal stent (FCSEMS) placement between January 2010 and July 2015 (10-mm-FCSEMS group). The overall survival (OS), the recurrent biliary obstruction (RBO), cause of RBO, time to RBO (TRBO) and adverse events in 12-mm-CSEEMS group and 10-mm-FCSEMS group were evaluated retrospectively. Results The OS tended to be longer in the 12-mm-CSEEMS group (log rank, P = 0.081) and TRBO was significantly longer in the 12-mm-CSEEMS group (log rank, P = 0.001) than in the 10-mm-FCSEMS group. Both univariate (HR, 0.449; 95 % CI, 0.27967 – 0.72215; P = 0.001) and multivariate (HR, 0.458; 95 % CI, 0.28395 – 0.73744; P = 0.001) Cox hazard analysis found that risk of RBO was significantly lower in 12-mm CSEEMS than in 10-mm FCSEMS. There were no significant differences between the 12-mm-CSEEMS group and 10-mm-FCSEMS group regarding the cause of RBO and adverse events. Conclusions The 12-mm CSEEMS showed a low risk of RBO compared with 10-mm FCSEMS and was considered to be effective and safe for draining unresectable malignant distal biliary obstruction.