Estimand framework and intercurrent events handling for clinical trials with time-to-event outcomes
This provides methodological guidance for clinical trial researchers dealing with time-to-event data, though it is an incremental extension of existing frameworks.
The paper addresses the lack of guidance in ICH E9(R1) for handling intercurrent events in clinical trials with time-to-event outcomes by defining estimands using potential outcomes and proposing six strategies, including a new competing-risk approach.
The ICH E9(R1) guideline presents a framework of estimand for clinical trials, proposes five strategies for handling intercurrent events (ICEs), and provides a comprehensive discussion and many real-life clinical examples for quantitative outcomes and categorical outcomes. However, in ICH E9(R1) the discussion is lacking for time-to-event (TTE) outcomes. In this paper, we discuss how to define estimands and how to handle ICEs for clinical trials with TTE outcomes. Specifically, we discuss six ICE handling strategies, including those five strategies proposed by ICH E9(R1) and a new strategy, the competing-risk strategy. Compared with ICH E9(R1), the novelty of this paper is three-fold: (1) the estimands are defined in terms of potential outcomes, (2) the methods can utilize time-dependent covariates straightforwardly, and (3) the efficient estimators are discussed accordingly.