title: Covered self-expandable metal stents with an anti-migration system improve patency duration without increased complications compared with uncovered stents for distal biliary obstruction caused by pancreatic carcinoma: a randomized multicenter trial.
abstract: OBJECTIVE
  The requirements of biliary stents used in the palliation of malignant biliary obstruction are a long duration of patency and minimal adverse effects. Covered self-expandable metal stents (SEMSs) have been shown to prevent tumor ingrowth, which is the most frequent complication of uncovered SEMSs. However, because they are prone to migration, the superiority of covered SEMS has yet to be convincingly demonstrated. The aim of this study was to evaluate the superiority of covered over uncovered SEMSs in the palliation of distal biliary obstruction due to unresectable pancreatic carcinoma, using both stent types with relatively low axial force and uncovered flared ends to prevent their migration.
  
  
  METHODS
  From April 2009 to December 2010, 120 patients who were admitted to 22 tertiary-care centers because of distal biliary obstruction from unresectable pancreatic carcinomas were enrolled in this prospective randomized multicenter study. Patients were randomly assigned to receive a covered or uncovered SEMS deployed at the site of the biliary stricture during endoscopic retrograde cholangiopancreatography. Stent patency time, patient survival time, patient survival time without stent dysfunction (time to stent dysfunction or patient death), cause of stent dysfunction (ingrowth, overgrowth, migration, or sludge formation), and serious adverse events were compared between covered and uncovered SEMS groups.
  
  
  RESULTS
  Patient survival time in the two groups did not significantly differ (median: 285 and 223 days, respectively; P=0.68). Patient survival time without stent dysfunction was significantly longer in the covered than in the uncovered SEMS group (median: 187 vs. 132 days; P=0.043). Stent patency was also significantly longer in the covered than in the uncovered SEMS group (mean±s.d.: 219.3±159.1 vs. 166.9±124.9 days; P=0.047). Reintervention for stent dysfunction was performed in 14 of 60 patients with covered SEMSs (23%) and in 22 of 60 patients with uncovered SEMSs (37%; P=0.08). Stent dysfunction was caused by tumor ingrowth, tumor overgrowth, and sludge formation in 0 (0%), 3 (5%), and 11 (18%) patients in the covered SEMSs group, and in 15 (25%), 2 (3%), and 6 (10%) patients in the uncovered SEMSs group, respectively. Stent migration was not observed in either group. Rates of tumor overgrowth and sludge formation did not significantly differ between the two groups, whereas the rate of tumor ingrowth was significantly lower in the covered than in the uncovered SEMS group (P<0.01). Acute pancreatitis occurred in only one patient in the covered SEMS group. Acute cholecystitis occurred in one patient in the covered SEMS group and in two patients in the uncovered SEMS group. There was no significant difference between the two groups in the incidence of serious adverse events.
  
  
  CONCLUSIONS
  By preventing tumor ingrowth and migration, covered SEMSs with an anti-migration system had a longer duration of patency than uncovered SEMSs, which recommends their use in the palliative treatment of patients with biliary obstruction due to pancreatic carcinomas.
authors.affiliation: Department of Gastroenterology and Hepatology, Kinki University, Osaka-sayama, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kitano
authors.forename: Yukitaka
authors.initials: Y
authors.lastname: Yamashita
authors.forename: Kiyohito
authors.initials: K
authors.lastname: Tanaka
authors.forename: Hideyuki
authors.initials: H
authors.lastname: Konishi
authors.forename: Shujiro
authors.initials: S
authors.lastname: Yazumi
authors.forename: Yoshitaka
authors.initials: Y
authors.lastname: Nakai
authors.forename: Osamu
authors.initials: O
authors.lastname: Nishiyama
authors.forename: Hiroyuki
authors.initials: H
authors.lastname: Uehara
authors.forename: Akira
authors.initials: A
authors.lastname: Mitoro
authors.forename: Tsuyoshi
authors.initials: T
authors.lastname: Sanuki
authors.forename: Makoto
authors.initials: M
authors.lastname: Takaoka
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Koshitani
authors.forename: Yoshifumi
authors.initials: Y
authors.lastname: Arisaka
authors.forename: Masatsugu
authors.initials: M
authors.lastname: Shiba
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Hoki
authors.forename: Hideki
authors.initials: H
authors.lastname: Sato
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Sasaki
authors.forename: Masako
authors.initials: M
authors.lastname: Sato
authors.forename: Kazunori
authors.initials: K
authors.lastname: Hasegawa
authors.forename: Hideaki
authors.initials: H
authors.lastname: Kawabata
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Okabe
authors.forename: Hidekazu
authors.initials: H
authors.lastname: Mukai
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D002277:Carcinoma / Q000150:complications / Q000401:mortality / Q000601:surgery*; D002779:Cholestasis / Q000209:etiology / Q000401:mortality / Q000601:surgery*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000150:complications / Q000401:mortality / Q000601:surgery*; D011475:Prosthesis Failure; D019919:Prosthesis Implantation; D015607:Stents; D015996:Survival Rate; D016896:Treatment Outcome