Hamada Tsuyoshi, Nakai Yousuke, Isayama Hiroyuki, Togawa Osamu, Kogure Hirofumi, Kawakubo Kazumichi, Tsujino Takeshi, Sasahira Naoki, Hirano Kenji, Yamamoto Natsuyo, Ito Yukiko, Sasaki Takashi, Mizuno Suguru, Toda Nobuo, Tada Minoru, Koike Kazuhiko
Department of Gastroenterology, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
Dig Endosc. 2014 Mar;26(2):270-5. doi: 10.1111/den.12120. Epub 2013 May 8.
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.
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.
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.
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.
自膨式金属支架（SEMS）置入术广泛应用于远端恶性胆管梗阻，生存分析用于评估SEMS功能障碍的累积发生率（如Kaplan-Meier[KM]法和对数秩检验）。然而，在存在“竞争风险”（此处指无SEMS功能障碍的死亡）的情况下，这些统计方法可能并不适用，因为这会影响发生感兴趣事件（SEMS功能障碍）的概率；也就是说，死亡后就无法再观察到SEMS功能障碍。在SEMS研究中，很少进行竞争风险分析。
我们引入了竞争风险分析的概念，并使用假设数据和实际数据说明了其对SEMS结果评估的影响。我们的示例性研究纳入了476例因不可切除的远端恶性胆管梗阻而接受SEMS置入术的连续患者。
通过KM法得出的男性和女性患者SEMS功能障碍累积发生率之间的显著差异（对数秩检验P = 0.044）在应用竞争风险分析后消失（Gray检验P = 0.115）。相比之下，虽然通过KM法得出的接受化疗和未接受化疗患者的SEMS功能障碍累积发生率相似（对数秩检验P = 0.647），但在竞争风险分析中，未接受化疗组的SEMS功能障碍累积发生率显著更低（Gray检验P = 0.031）。
在估计SEMS功能障碍的累积发生率时，需要适当考虑死亡作为竞争风险事件，否则分析结果可能存在偏差。
