Roshanaei Ghodratollah, Kazemnejad Anoshirvan, Sadighi Sanambar
Biostatistics, Medical Sciences, Tarbiat Modares University, Tehran, Iran.
Asian Pac J Cancer Prev. 2011;12(9):2443-6.
In some survival studies, several events are taken into consideration. If the events are independent then the ordinary methods such as Kaplan-Meier, Cox or parametric models can be used. If one of the events dependently (informatively) censors the other, the results are biased. The present study was designed to assess the risk factors for recurrence of patients with gastric cancer in the presence of informative censoring using parametric models with a semi-competing risk approach.
In a retrospective study, 408 cases of gastric cancer were selected from the patients referred to the Tehran Cancer Institute from March 2003 to March 2007. Gender, age at diagnosis, distant metastasis, tumor size, histology type, tumor grade, pathologic stage, tumor site, and type of treatment were studied as prognostic factors and used in the models. Parametric models such as Weibull, exponential, log-logistic were used with informative right censoring using Akaike Information Criteria (AIC) as criteria to compare models. The data were analyzed using R statistical software. A p-value of less than 0.05 was considered as statistically significant.
Based on Akaike information criteria (AIC), the Weibull model best fitted to data. The effect of tumor size and pathologic stage were significant on recurrence in both univariate and multivariate analyses. Tumor site and tumor grade were significant only in univariate analysis.
The results showed that semi-competing risk methods perform well in determining risk factors for disease recurrence.
在一些生存研究中，会考虑多个事件。如果这些事件相互独立，那么可以使用诸如Kaplan-Meier法、Cox法或参数模型等常规方法。如果其中一个事件对另一个事件产生依赖性（信息性）删失，结果就会产生偏差。本研究旨在使用具有半竞争风险方法的参数模型，评估存在信息性删失情况下胃癌患者复发的危险因素。
在一项回顾性研究中，从2003年3月至2007年3月转诊至德黑兰癌症研究所的患者中选取了408例胃癌病例。将性别、诊断时年龄、远处转移、肿瘤大小、组织学类型、肿瘤分级、病理分期、肿瘤部位和治疗类型作为预后因素进行研究，并用于模型中。使用Weibull模型、指数模型、对数逻辑模型等参数模型，并采用赤池信息准则（AIC）进行信息性右删失分析，以此作为比较模型的标准。数据使用R统计软件进行分析。p值小于0.05被认为具有统计学意义。
基于赤池信息准则（AIC），Weibull模型最适合该数据。在单变量和多变量分析中，肿瘤大小和病理分期对复发的影响均具有显著性。肿瘤部位和肿瘤分级仅在单变量分析中具有显著性。
结果表明，半竞争风险方法在确定疾病复发的危险因素方面表现良好。
