The role of intention to treat in analysis of noninferiority studies

In analysing clinical trials designed to show superiority of one treatment compared to another, it is standard to use an intention to treat analytic approach. In active-controlled noninferiority studies, this is not standard, due to concerns that such an analysis will inflate the chance of falsely rejecting the null hypothesis, accepting therapeutic noninferiority when it is not justified. The reasons for using intention to treat (ITT) approaches in superiority studies include a desire to capture all information on study subjects, a need to prevent bias, and assurance that comparative groups are, on average, equivalent in prognostic factors. In this commentary, we argue that these same justifications carry over to noninferiority studies, and that for those and other reasons it should be the preferred analytic approach. We review regulatory guidelines, and propose a number of approaches to minimizing the potential disadvantages of the ITT approach in the noninferiority setting.