Covered vs. uncovered self-expandable metal stents for malignant distal biliary strictures: a systematic review and meta-analysis

BACKGROUND: Self-expandable metal stents (SEMS) are used for palliation of distal malignant biliary strictures, but the role of covered SEMS is less clear. We performed an up-to-date meta-analysis to compare the performance of covered and uncovered SEMS in patients with unresectable distal malignant biliary strictures. METHODS: A computerized medical search was performed using MEDLINE, EMBASE, and the Cochrane Library between 2000 and December 2016 to identify all randomized trials that compared covered with uncovered SEMS in patients with distal malignant biliary strictures. Primary outcomes were stent failure and patient mortality; secondary outcomes were stent dysfunction and adverse events. Pooled estimates were computed using the random effects model. RESULTS: Overall, 11 RCTs involving 1272 patients were included. The primary outcomes of stent failure and patient mortality did not differ significantly between covered and uncovered SEMS (hazard ratio [HR] 0.68, 95 % confidence interval [CI] 0.40 - 1.17; HR 0.89, 95 %CI 0.76 - 1.05, respectively). However, stent migration and sludge formation were much more common with covered SEMS (odds ratio [OR] 5.11, 95 %CI 1.84 - 14.17; OR 2.46, 95 %CI 1.37 - 4.43). The use of covered SEMS was associated with a lower rate of tumor ingrowth (OR 0.21, 95 %CI 0.09 - 0.50) but a higher rate of tumor overgrowth (OR 2.00, 95 %CI 1.15 - 3.48) compared with uncovered stents. The rates of procedure-related adverse events were similar in both groups. CONCLUSION: There was a risk reduction of about 32 % for both stent failure and patient mortality with covered SEMS but this difference was not significant. Migration and sludge rates were higher with covered SEMS, whereas tumor ingrowth was more likely with uncovered SEMS. The data show no added benefit of covered SEMS; further stent evolution is desirable.