Risk-difference curves can be used to communicate time-dependent effects of adjuvant therapies for early stage cancer

Objectives: To describe the use of risk-difference curves for communicating time-dependent absolute treatment effects. Study Design and Setting: Three examples based on individual patient data meta-analyses for adjuvant treatments for early-stage breast cancer are presented. Unit record datasets were re-created from the published Kaplan-Meier curves and numbers at risk or person-years at risk. Risk-difference curves, with corresponding 95% confidence bands, are presented and discussed. Results: Risk-difference curves are useful for communicating the results from trials of adjuvant treatments for early-stage cancer when standard measures of the absolute treatment effect for survival data (ie, difference-in-mean and difference-in-median survival) can be difficult to estimate. They also avoid the problem of "evolving selection bias", which can affect interval-specific hazard ratio (HR)s in trials with long follow-up and where the participants are heterogeneous with respect to prognosis. Conclusion: Clinical epidemiologists should consider reporting risk-difference curves in addition to Kaplan-Meier curves and the HR. Crown Copyright (C) 2014 Published by Elsevier Inc. All rights reserved.