Testing equivalence of survival before but not after end of follow-up

Julie K. Furberg (), Christian B. Pipper () and Thomas Scheike ()
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Julie K. Furberg: Novo Nordisk A/S
Christian B. Pipper: LEO Pharma A/S
Thomas Scheike: University of Cophenagen

Lifetime Data Analysis: An International Journal Devoted to Statistical Methods and Applications for Time-to-Event Data, 2021, vol. 27, issue 2, No 2, 216-243

Abstract: Abstract For equivalence trials with survival outcomes, a popular testing approach is the elegant test for equivalence of two survival functions suggested by Wellek (Biometrics 49: 877–881, 1993). This test evaluates whether or not the difference between the true survival curves is practically irrelevant by specifying an equivalence margin on the hazard ratio under the proportional hazards assumption. However, this approach is based on extrapolating the behavior of the survival curves to the whole time axis, whereas in practice survival times are only observed until the end of follow-up. We propose a modification of Welleks test that only addresses equivalence until end of follow-up and derive the large sample properties of this test. Another issue is the proportional hazards assumption which may not be realistic. If this assumption is violated, one may severely misjudge the actual treatment effect with a hazard ratio quantification and wrongly declare equivalence. We suggest a non-parametric test for assessing survival equivalence within the follow-up period. We derive the large sample properties of this test and provide an approximation to the limiting distribution under some mild assumptions on the functional form of the difference between the two survival curves. Both suggestions are investigated by simulation and applied to a clinical trial on survival of gastric cancer patients.

Keywords: Equivalence testing; Survival data; Cox model; Proportional hazards assumption (search for similar items in EconPapers)
Date: 2021
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DOI: 10.1007/s10985-021-09517-5

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