Intention-to-Treat Comparisons in Randomized Trials

Intention-to-treat (ITT) comparisons have a central place in reporting on randomized controlled trials, though there are typically additional analyses of interest such as those making adjustments for nonadherence. In our ITT reporting of results from the Women’s Health Initiative (WHI) randomized trials we have relied primarily on highly flexible hazard ratio (Cox) regression methods. However, these methods, especially the proportional hazards special case, have been criticized for being difficult to interpret and frequently oversimplified, and for not being consistent with modern causality theories using potential outcomes. Here we address these topics and extend our use of hazard rate methods for ITT comparisons in the WHI trials.