A prospective randomised study of "covered" versus "uncovered" diamond stents for the management of distal malignant biliary obstruction

Abstract

Background and aim: Covered self-expandable metal stents (EMS) were recently developed to overcome tumour ingrowth in conventional EMS. However, supporting evidence for the efficacy of covered EMS is lacking.

Patients and methods: We enrolled 112 patients with unresectable distal biliary malignancies. They were randomly assigned to polyurethane covered (n = 57) or original diamond stent (n = 55).

Results: Stent occlusion occurred in eight patients (14%) after a mean of 304 days in the covered group, and in 21 patients (38%) after a mean of 166 days in the uncovered group. The incidence of covered EMS occlusion was significantly lower than that of uncovered EMS (p = 0.0032). The cumulative stent patency of covered stents was significantly higher than that of uncovered stents (p = 0.0066). No tumour ingrowth occurred in the covered group while it was observed in 15 patients in the uncovered group. In subgroup analysis, the cumulative patency of the covered EMS was significantly higher in pancreatic cancer (p = 0.0363) and metastatic lymph nodes (p = 0.0354). There was no significant difference in survival between the two groups. Acute cholecystitis was observed in two of the covered group and in none of the uncovered group. Mild pancreatitis occurred in five of the covered group and in one of the uncovered group.

Conclusions: Covered diamond stents successfully prevented tumour ingrowth and were significantly superior to uncovered stents for the treatment of patients with distal malignant biliary obstruction. However, careful attention must be paid to complications specific to covered self-expandable metal stents, such as acute cholecystitis and pancreatitis.

Figures

Figure 1

Covered diamond stent (Microvasive; Boston Scientific Corporation, Natik, Massachusetts, USA). The stents used in this study were 10 mm in width and 60 or 80 mm in length, with the length determined on the basis that the covered portion should be at least 20 mm longer than the stenotic lesion. The stent was partially covered with polyurethane. The thickness of the covered membrane was 50–60 μm. The stents were left uncovered for 5 mm from both ends to prevent their migration or movement.

Figure 2

Kaplan-Meier graph showing survival of the patients. No significant difference was observed between the covered and uncovered groups. EMS, self-expandable metallic stents.

Figure 3

Kaplan-Meier graph showing cumulative patency. Stent patency was significantly higher (p = 0.0066) in the covered group than in the uncovered group. EMS, self-expandable metallic stents.

Figure 4

Kaplan-Meier graph showing cumulative patency in patients with pancreatic cancer. Stent patency was significantly higher (p = 0.0363) in the covered group than in the uncovered group. EMS, self-expandable metallic stents.

Figure 5

Kaplan-Meier graph showing cumulative patency in patients with metastatic lymph nodes. Stent patency was significantly higher (p = 0.0354) in the covered group than in the uncovered group. EMS, self-expandable metallic stents.