Assessing contribution of treatment phases through tipping point analyses via counterfactual elicitation using rank preserving structural failure time models

TL;DR

This paper introduces a new statistical method combining tipping point analysis and RPSFT modeling to evaluate the contribution of individual treatment phases in multi-phase cancer therapies, aiding clinical decision-making.

Contribution

It develops a novel approach integrating tipping point analysis with RPSFT models to assess treatment phase contributions in complex regimens, addressing limitations of traditional methods.

Findings

Method successfully applied to phase 3 cancer trial data

Provides interpretable indices of treatment phase contribution

Offers practical guidelines for implementation

Abstract

This article provides a novel approach to assess the importance of specific treatment phases within a treatment regimen through tipping point analyses (TPA) of a time-to-event endpoint using rank-preserving-structural-failure-time (RPSFT) modelling. In oncology clinical research, an experimental treatment is often added to the standard of care therapy in multiple treatment phases to improve patient outcomes. When the resulting new regimen provides a meaningful benefit over standard of care, gaining insights into the contribution of each treatment phase becomes important to properly guide clinical practice. New statistical approaches are needed since traditional methods are inadequate in answering such questions. RPSFT modelling is an approach for causal inference, typically used to adjust for treatment switching in randomized clinical trials with time-to-event endpoints. A tipping-point analysis is commonly used in situations where a statistically significant treatment effect is suspected to be an artifact of missing or unobserved data rather than a real treatment difference. The methodology proposed in this article is an amalgamation of these two ideas to investigate the contribution of a specific component of a regimen comprising multiple treatment phases. We provide different variants of the method and construct indices of contribution of a treatment phase to the overall benefit of a regimen that facilitates interpretation of results. The proposed approaches are illustrated with findings from a recently concluded, real-life phase 3 cancer clinical trial. We conclude with several considerations and recommendations for practical implementation of this new methodology.