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Long‐term survival with non‐proportional hazards: results from the Dutch Gastric Cancer Trial
Author(s) -
Putter H.,
Sasako M.,
Hartgrink H. H.,
van de Velde C. J. H.,
van Houwelingen J. C.
Publication year - 2005
Publication title -
statistics in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.996
H-Index - 183
eISSN - 1097-0258
pISSN - 0277-6715
DOI - 10.1002/sim.2143
Subject(s) - proportional hazards model , term (time) , cancer , survival analysis , medicine , oncology , statistics , mathematics , physics , quantum mechanics
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. Copyright © 2005 John Wiley & Sons, Ltd.