title: Risk-difference curves can be used to communicate time-dependent effects of adjuvant therapies for early stage cancer.
abstract: OBJECTIVE
  To describe the use of risk-difference curves for communicating time-dependent absolute treatment effects.
  
  
  METHODS
  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.
  
  
  CONCLUSIONS
  Clinical epidemiologists should consider reporting risk-difference curves in addition to Kaplan-Meier curves and the HR.
authors.affiliation: Clinical Epidemiology and Biostatistics Unit, Murdoch Children's Research Institute, Royal Children's Hospital, Flemington Road, Parkville, Melbourne, Victoria 3052, Australia; Department of Paediatrics, Royal Children's Hospital, Flemington Road, Parkville, Melbourne, Victoria 3052, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Coory
authors.affiliation: Clinical Epidemiology and Biostatistics Unit, Murdoch Children's Research Institute, Royal Children's Hospital, Flemington Road, Parkville, Melbourne, Victoria 3052, Australia; Department of Paediatrics, Royal Children's Hospital, Flemington Road, Parkville, Melbourne, Victoria 3052, Australia. Electronic address: karen.lamb@mcri.edu.au.
authors.forename: Karen E
authors.initials: KE
authors.lastname: Lamb
authors.affiliation: Department of Clinical Pharmacology, School of Medicine, Flinders University, Bedford Park, South Australia 5042, Australia.
authors.forename: Michael
authors.initials: M
authors.lastname: Sorich
mesh_terms: D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000473:pathology / Q000628:therapy*; D003131:Combined Modality Therapy; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D053208:Kaplan-Meier Estimate; D008297:Male; D015201:Meta-Analysis as Topic; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000473:pathology; D009367:Neoplasm Staging
keywords: Absolute treatment effect; Difference-in-mean survival; Difference-in-median survival; Hazard ratio; Kaplan-Meier curves; Relative treatment effect; Risk-difference curve; Survival; Time-dependent treatment effect