title: Estimation and comparison of cumulative incidences of biliary self-expandable metallic stent dysfunction accounting for competing risks.
abstract: BACKGROUND
  Self-expandable metallic stent (SEMS) placement is widely carried out for distal malignant biliary obstruction, and survival analysis is used to evaluate the cumulative incidences of SEMS dysfunction (e.g. the Kaplan-Meier [KM] method and the log-rank test). However, these statistical methods might be inappropriate in the presence of 'competing risks' (here, death without SEMS dysfunction), which affects the probability of experiencing the event of interest (SEMS dysfunction); that is, SEMS dysfunction can no longer be observed after death. A competing risk analysis has rarely been done in studies on SEMS.
  
  
  METHODS
  We introduced the concept of a competing risk analysis and illustrated its impact on the evaluation of SEMS outcomes using hypothetical and actual data. Our illustrative study included 476 consecutive patients who underwent SEMS placement for unresectable distal malignant biliary obstruction.
  
  
  RESULTS
  A significant difference between cumulative incidences of SEMS dysfunction in male and female patients via theKM method (P = 0.044 by the log-rank test) disappeared after applying a competing risk analysis (P = 0.115 by Gray's test). In contrast, although cumulative incidences of SEMS dysfunction via the KM method were similar with and without chemotherapy (P = 0.647 by the log-rank test), cumulative incidence of SEMS dysfunction in the non-chemotherapy group was shown to be significantly lower (P = 0.031 by Gray's test) in a competing risk analysis.
  
  
  CONCLUSIONS
  Death as a competing risk event needs to be appropriately considered in estimating a cumulative incidence of SEMS dysfunction, otherwise analytical results may be biased.
authors: Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors: Tsuyoshi
authors: T
authors: Hamada
authors: Yousuke
authors: Y
authors: Nakai
authors: Hiroyuki
authors: H
authors: Isayama
authors: Osamu
authors: O
authors: Togawa
authors: Hirofumi
authors: H
authors: Kogure
authors: Kazumichi
authors: K
authors: Kawakubo
authors: Takeshi
authors: T
authors: Tsujino
authors: Naoki
authors: N
authors: Sasahira
authors: Kenji
authors: K
authors: Hirano
authors: Natsuyo
authors: N
authors: Yamamoto
authors: Yukiko
authors: Y
authors: Ito
authors: Takashi
authors: T
authors: Sasaki
authors: Suguru
authors: S
authors: Mizuno
authors: Nobuo
authors: N
authors: Toda
authors: Minoru
authors: M
authors: Tada
authors: Kazuhiko
authors: K
authors: Koike
mesh_terms: D001650:Bile Duct Neoplasms / Q000150:complications* / Q000401:mortality / Q000601:surgery; D002779:Cholestasis / Q000453:epidemiology* / Q000209:etiology; D019544:Equipment Failure Analysis / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D007564:Japan / Q000453:epidemiology; D008297:Male; D010166:Palliative Care / Q000379:methods*; D010190:Pancreatic Neoplasms / Q000150:complications* / Q000401:mortality / Q000601:surgery; D011379:Prognosis; D011475:Prosthesis Failure; D012189:Retrospective Studies; D012307:Risk Factors; D015607:Stents; D015996:Survival Rate / Q000639:trends
keywords: competing risk; distal malignant biliary obstruction; dysfunction; self-expandable metallic stent (SEMS)