Self-expandable metal stents versus plastic stents for malignant biliary obstruction: a meta-analysis

Background Malignant biliary obstruction frequently portends a poor prognosis. Palliative treatment with stenting is often required to alleviate symptoms and potentially prevent adverse events. Objectives The aims of our study were (1) to evaluate the clinical difference between self-expandable metal stents (SEMSs) and plastic stents (PSs) in both hilar and distal malignant biliary obstruction on occlusion rate and 30-day mortality rate (primary outcomes) and stent insertion success rate, therapeutic failure, reintervention rate, and adverse events (secondary outcomes); (2) to compare unilateral stenting with bilateral stenting in hilar malignant obstruction in terms of occlusion rate and 30-day mortality rate (primary outcomes) and insertion success rate, therapeutic failure, and adverse events (secondary outcomes). Methods PubMed, Embase, and Cochrane databases were searched for studies that provided data about malignant biliary obstruction and stent therapy. We included randomized, controlled trials (RCT), prospective observational cohort, and retrospective case-control studies. The quality of each included RCT study was assessed by the Jadad scale. Mantel-Haenszel odds ratios (ORs) and mean differences were calculated by using a random-effects model. Results Nineteen studies involving 1989 patients (1045 SEMSs and 944 PSs) were included for the comparison of SEMSs and PSs. We also included 7 studies that compared unilateral with bilateral stenting involving 634 patients (346 unilateral and 268 bilateral). Our meta-analysis confirmed that SEMSs are associated with a statistically significant lower risk of occlusion compared with PSs in the short term (OR 0.27; 95% confidence interval [CI], 0.13-0.60) and long term (OR 0.38; 95% CI, 0.28-0.53). SEMSs had a lower 30-day occlusion rate than PSs in both hilar malignant obstruction (OR 0.16; 95% CI, 0.04-0.62) and distal malignant obstruction (OR 0.36; 95% CI, 0.14-0.93). SEMSs had a lower long-term occlusion rate compared with PSs in hilar malignant obstruction (OR 0.28; 95% CI, 0.19-0.39) and distal malignant obstruction (OR 0.42; 95% CI, 0.27-0.64). The 30-day mortality rate was similar with SEMSs and PSs (OR 0.74; 95% CI, 0.47-1.17). Therapeutic failure was more likely when using PSs (13%) compared with SEMSs (7%) (OR 0.43; 95% CI, 0.27-0.67). SEMSs required fewer reinterventions compared with PSs (mean difference, -0.49; 95% CI, -0.8 to -0.19). The incidence of cholangitis was statistically lower with SEMSs (8% vs 21%) (OR 0.41; 95% CI, 0.22-0.76). Bilateral stenting for hilar obstruction was not associated with a lower obstruction rate than unilateral stenting (OR 1.49; 95% CI, 0.77-2.89) or a lower 30-day mortality rate (OR 0.73; 95% CI, 0.29-1.79). There was no statistical difference in therapeutic failure (OR 1.47; 95% CI, 0.77-2.89) or cholangitis incidence (OR 0.61; 95% CI, 0.27-1.38). Conclusion SEMSs are associated with a statistically significantly lower occlusion rate, less therapeutic failure, less need for reintervention, and lower cholangitis incidence. There was no statistically significant difference in occlusion rate, therapeutic failure, and cholangitis incidence with bilateral stenting. Guideline recommendations may need to be modified to reflect clear and compelling data demonstrating the benefit of SEMSs in patients with malignant biliary obstruction. Bilateral stenting should be avoided because it has no benefit over unilateral stenting in terms of occlusion rate or therapeutic failure.