A Causal Perspective on "Appropriate Implementation of ICH E9(R1) Addendum Strategies" (Comment on Fleming et al.)

This commentary offers perspectives on delivering "rigorous causal inference on meaningful estimands" that differ from the opinions recently shared by Fleming et al. We (1) depict a more robust pathway for achieving this aim that incorporates clinical, causal and statistical reasoning, (2) suggest a tangibility criterion to judge the practical usefulness of an intercurrent event strategy, (3) illustrate the utility of causal inference methods in providing robust estimates when the clinical objective aligns with a hypothetical strategy, and (4) advocate for careful consideration of the tradeoffs between an estimand's relevance and the required assumptions.