In a placebo-controlled clinical study one may calculate the average treatment effect to convey the effect of the active treatment on some outcome. However, if it is speculated that the treatment only has an effect if the patient responds to the treatment defined by a certain biomarker response, then it is arguably more relevant to estimate the treatment effect among such responders. We present such a causal parameter that is based on principal stratification and is identified under the exclusion of a treatment effect among the nonresponders. We focus on time-to-event outcomes allowing for right censoring, and construct a doubly robust and efficient estimator based on the associated efficient influence function. The properties of the estimator are showcased in a simulation study and the methodology is applied to the Leader trial investigating the effect of liraglutide on the occurrence of cardiovascular events.

中文翻译：

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通过事件发生时间终点评估治疗反应者的治疗效果

在安慰剂对照临床研究中，人们可以计算平均治疗效果，以传达积极治疗对某些结果的影响。然而，如果推测只有当患者对由某种生物标志物反应定义的治疗有反应时，治疗才有效，那么估计此类反应者中的治疗效果可能更相关。我们提出了这样一个因果参数，该参数基于主要分层，并在排除无反应者中的治疗效果的情况下进行识别。我们专注于事件发生的时间结果，允许正确的审查，并基于相关的有效影响函数构建一个双重稳健和高效的估计器。模拟研究展示了估计器的特性，并将该方法应用于研究利拉鲁肽对心血管事件发生的影响的 Leader 试验。