# Adaptations and Heterogeneity of Treatment Effects in Platform Trials—Protocol for Two Methodological Studies

## TL;DR

This paper outlines two studies to examine methods for assessing treatment effect differences and adaptations in complex adaptive platform trials.

## Contribution

The studies will systematically evaluate methodological approaches for HTE and adaptations in adaptive platform trials.

## Key findings

- Study I will assess methods used to evaluate heterogeneity of treatment effects.
- Study II will assess adaptations and stopping rules in included trials.
- The findings will help improve the design of adaptive platform trials.

## Abstract

Adaptive platform trials bring opportunities for improved infrastructure and effective advancement in medical care but are methodologically complex. Assessment of heterogeneity of treatment effects (HTE) according to participant characteristics and adaptations, including adaptive stopping, are important methodological features in these trials, which may be approached in multiple ways. We aim to characterise the assessment of HTE and use of adaptations, including their key methodological features, in adaptive platform trials.

This protocol outlines two methodological studies, which will be based on a common, systematic literature search and data extraction. We will include adaptive platform trials conducted from 2005 onwards. Screening and data extraction will be performed independently and in duplicate. In Study I, we will assess methods used to evaluate HTE, and in Study II, we will assess adaptations and stopping rules in the included trials.

The two proposed methodological studies will provide an overview of important methodological features regarding the assessment of HTE and adaptations used in adaptive platform trials. Better knowledge of available methods to assess these features can improve the conditions for designing adaptive platform trials and identify areas for further development.