The nph2ph-transform: applications to the statistical analysis of completed clinical trials

TL;DR

This paper introduces the nph2ph transform, a method that converts non-proportional hazards models into proportional hazards models, enabling easier analysis of complex treatment effects in clinical trials.

Contribution

The paper presents a novel transform that simplifies the analysis of non-proportional hazards in clinical trial data by converting them into proportional hazards models.

Findings

The nph2ph transform often admits simple approximations.

The transform enables the use of standard PH techniques on NPH data.

Application to clinical trials provides new insights into treatment effects.

Abstract

We present several illustrations from completed clinical trials on a statistical approach that allows us to gain useful insights regarding the time dependency of treatment effects. Our approach leans on a simple proposition: all non-proportional hazards (NPH) models are equivalent to a proportional hazards model. The nph2ph transform brings an NPH model into a PH form. We often find very simple approximations for this transform, enabling us to analyze complex NPH observations as though they had arisen under proportional hazards. Many techniques become available to us, and we use these to understand treatment effects better.