A Randomized Trial Comparing the Covered and Uncovered Wallstent in the Palliation of Malignant Distal Biliary Obstruction: Interim Analysis

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Background: Covered and uncovered Wallstents (Boston Scientific Endoscopy) are used to palliate malignant biliary obstruction. Differences in efficacy or safety have not been prospectively evaluated in a randomized trial. Methods: Patients with distal malignant biliary obstruction who were not surgical candidates were randomly assigned at ERCP to receive a covered or uncovered Wallstent. Telephone interviews were conducted at one week and then monthly following stent placement for symptoms of stent obstruction, medical interventions and hospitalizations. Outcomes were stent obstruction, survival and serious adverse events (SAE) defined as requiring hospitalization, procedure or resulting in death. Patients and interviewers were blinded to stent assignment. To determine a 20% difference between the two groups with an alpha error of 0.05 and a beta-error of 0.10, 276 patients were required. An interim analysis was scheduled 6 months after the first 100 patients had been randomized. Time to stent obstruction or death was determined using the log-rank test; patients were censored if they were lost to follow-up or alive with a patent stent at their last follow-up interview. SAEs in each group were compared using the Chi-square test. The analysis was intention-to-treat. Results: 100 patients were randomized at 4 sites between 10/2002 and 05/2006. Mean age was 66 years (SD 13) and 52 were male. 84% had pancreatic cancer. Stent obstruction occurred in 7/49 (14%)and 10/51 (20%) in the uncovered and covered Wallstent group, respectively. Of these 17 patients, the median time to stent obstruction was 224 days (range 50-711) and 273 days (range 9-357) in the uncovered and covered Wallstent groups, respectively (p = 0.67). Of the remaining 83 patients, 61 died, 11 were lost to follow-up and 11 are alive. The median time to stent obstruction or death was 217 days (95%CI 102-313)and 236 days (95%CI 117-290)in the uncovered and covered Wallstent group, respectively(p = 0.67). A total of 118 SAEs ocurred in 49 patients. Twenty (41%) and 29 (59%) patients had a SAE in the uncovered and covered Wallstent group, respectively (p = 0.11). Twelve (25%) and 15 (29%) patients had a SAE possibly-related to the ERCP or stent in the uncovered and covered Wallstent group, respectively (p = 0.58). Two patients in each group developed cholecystitis. Four patients were noted to have a migrated stent; all were in the covered stent group. Conclusion: This interim analysis did not demonstrate a difference in duration of stent patency, survival or SAEs between the covered and uncovered Wallstent in the palliation of malignant distal biliary obstruction.