title: Long-term survival with non-proportional hazards: results from the Dutch Gastric Cancer Trial.
abstract: Randomized clinical trials with long-term survival data comparing two treatments often show Kaplan-Meier plots with crossing survival curves. Such behaviour implies a violation of the proportional hazards assumption for treatment. The Cox proportional hazards regression model with treatment as a fixed effect can therefore not be used to assess the influence of treatment of survival. In this paper we analyse long-term follow-up data from the Dutch Gastric Cancer Trial, a randomized study comparing limited (D1) lymph node dissection with extended (D2) lymph node dissection. We illustrate a number of ways of dealing with survival data that do not obey the proportional hazards assumption, each of which can be easily implemented in standard statistical packages.
authors.affiliation: Department of Medical Statistics and Bioinformatics, Leiden University Medical Centre, University of Leiden, The Netherlands. h.putter@lumc.nl
authors.forename: H
authors.initials: H
authors.lastname: Putter
authors.forename: M
authors.initials: M
authors.lastname: Sasako
authors.forename: H H
authors.initials: HH
authors.lastname: Hartgrink
authors.forename: C J H
authors.initials: CJ
authors.lastname: van de Velde
authors.forename: J C
authors.initials: JC
authors.lastname: van Houwelingen
mesh_terms: D000368:Aged; D001699:Biometry; D005260:Female; D006801:Humans; D008197:Lymph Node Excision / Q000379:methods; D008297:Male; D008875:Middle Aged; D009426:Netherlands / Q000453:epidemiology; D016016:Proportional Hazards Models; D011446:Prospective Studies; D016032:Randomized Controlled Trials as Topic / Q000706:statistics & numerical data*; D013274:Stomach Neoplasms / Q000401:mortality* / Q000601:surgery*; D015996:Survival Rate