Sample-size formula for clustered survival data using weighted log-rank statistics

Ronald E. Gangnon

Biometrika, 2004, vol. 91, issue 2, 263-275

Abstract: We present a simple sample-size formula for weighted log-rank statistics applied to clustered survival data with variable cluster sizes and arbitrary treatment assignments within clusters. This formula is based on the asymptotic normality of weighted log-rank statistics under certain local alternatives in the clustered data context. We also provide consistent variance estimators. The derived sample-size formula reduces to Schoenfeld's (1983) formula for cases of no clustering or independence within clusters. Simulation results verify control of the Type I error and accuracy of the sample-size formula. Use of the sample-size formula in an event-driven clinical trial design is illustrated using data from the Early Treatment Diabetic Retinopathy Study. Copyright Biometrika Trust 2004, Oxford University Press.

Date: 2004
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