Teasing out the overall survival benefit with adjustment for treatment switching to other therapies

TL;DR

This paper reviews and proposes advanced statistical methods to accurately estimate the true overall survival benefit of experimental cancer treatments in clinical trials, accounting for complex treatment switching scenarios.

Contribution

It introduces two new methods, stratified RPSFTM and random-forest-based prediction, to improve survival benefit estimation when patients switch treatments.

Findings

Existing methods struggle with complex switching scenarios.

Simulation shows proposed methods outperform traditional approaches.

New methods provide more accurate survival benefit estimates.

Abstract

In oncology clinical trials, characterizing the long-term overall survival (OS) benefit for an experimental drug or treatment regimen (experimental group) is often unobservable if some patients in the control group switch to drugs in the experimental group and/or other cancer treatments after disease progression. A key question often raised by payers and reimbursement agencies is how to estimate the true benefit of the experimental drug group on overall survival that would have been estimated if there were no treatment switches. Several commonly used statistical methods are available to estimate overall survival benefit while adjusting for treatment switching, ranging from naive exclusion or censoring approaches to more advanced methods including inverse probability of censoring weighting (IPCW), iterative parameter estimation (IPE) algorithm or rank-preserving structural failure time models (RPSFTM). However, many clinical trials now have patients switching to different treatment regimens other than the test drugs, and the existing methods cannot handle more complicated scenarios. To address this challenge, we propose two additional methods: stratified RPSFTM and random-forest-based prediction. A simulation study is conducted to assess the properties of the existing methods along with the two newly proposed approaches.