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Abstract:
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The validation of surrogate endpoints has been initially studied by Prentice and Freedman. Noting operational difficulties, Buyse and Molenberghs proposed instead to use jointly the within-treatment partial association of true and surrogate responses, and the treatment effect on the surrogate relative to that on the true outcome. In a multicenter setting, these quantities can be generalized to individual-level and trial-level measures of surrogacy. Buyse and colleagues have proposed a meta-analytic framework to study surrogacy at the trial and individual-patient levels. Variations for various endpoints have been developed. Efforts have been made to converge to a common framework. This includes a so-called variance reducation factor and an information-theoretic approach. Work has been done regarding sample size assessment, leading to the surrogate threshold effect.
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