Best period to replace or change plastic stents with self-expandable metallic stents using multivariate competing risk regression analysis

In endoscopic biliary drainage (EBD) for various benign and malignant biliary disorders, the appropriate timing to replace or change a plastic stent (PS) with a self-expandable metallic stent (SEMS) remains unclear. This study aimed to define the best period to replace or change a PS with a SEMS. Between January 1, 2012, and December 31, 2018, 1,887 consecutive EBD procedures, including 170 SEMS placements, were retrospectively identified. The period to recurrent biliary obstruction (PRBO) was estimated and compared between the malignant and benign groups and according to each disease using time to event analysis and competing risk analysis. Compared with the benign group, the malignant group had significantly shorter median PRBO with interquartile range (IQR) after PS placement [108 (39 - 270) vs. 613 (191 - 1,329) days, P<0.001], even on multivariate analysis, with a subdistribution hazard ratio (SHR) of 3.58 (P<0.001). The shortest PRBO distribution from the first quartile of the non-RBO period was seen in Mirizzi syndrome cases (25 days, P=0.030, SHR=3.32) in the benign group and in cases of pancreatic cancer (32 days, P=0.041, SHR=2.06); perihilar bile duct cancer (27 days, P=0.006, SHR=2.69); and ampullary cancer (22 days, P=0.001, SHR=3.78) in the malignant group. Our study supports that stent replacement for the benign group is feasible after 6 months, and the best period to replace or change a PS with a SEMS should be decided on the basis of the underlying disease to prevent RBO.