In recent years, the use of adaptive methods in clinical development based on accrued data has become very popular due to its flexibility in modifying trial procedures and / or statistical procedures of on-going clinical trials. However, it is a concern that the actual patient population after the modi. cations could deviate from the originally targeted patient population. Major modi. cations of trial procedures and / or statistical procedures of on-going trials may result in a totally different trial, which is unable to address the scientific/medical questions that the trial intends to answer. In this article, the impact on the target patient population, statistical inference, and power analysis for sample size adjustment after changes or modi. cations made to an on-going clinical trial is studied.
