  Randomized controlled trials (RCT) are the gold standard for evaluation of
the efficacy and safety of investigational interventions. If every patient in
an RCT were to adhere to the randomized treatment, one could simply analyze the
complete data to infer the treatment effect. However, intercurrent events
(ICEs) including the use of concomitant medication for unsatisfactory efficacy,
treatment discontinuation due to adverse events, or lack of efficacy, may lead
to interventions that deviate from the original treatment assignment.
Therefore, defining the appropriate estimand (the appropriate parameter to be
estimated) based on the primary objective of the study is critical prior to
determining the statistical analysis method and analyzing the data. The
International Council for Harmonisation (ICH) E9 (R1), published on November
20, 2019, provided 5 strategies to define the estimand: treatment policy,
hypothetical, composite variable, while on treatment and principal stratum. In
this article, we propose an estimand using a mix of strategies in handling
ICEs. This estimand is an average of the null treatment difference for those
with ICEs potentially related to safety and the treatment difference for the
other patients if they would complete the assigned treatments. Two examples
from clinical trials evaluating anti-diabetes treatments are provided to
illustrate the estimation of this proposed estimand and to compare it with the
estimates for estimands using hypothetical and treatment policy strategies in
handling ICEs.
