title: Sample Size Requirements and Study Duration for Testing Main Effects and Interactions in Completely Randomized Factorial Designs When Time to Event is the Outcome.
abstract: In this paper we develop the methodology for designing clinical trials with any factorial arrangement when the primary outcome is time to event. We provide a matrix formulation for calculating the sample size and study duration necessary to test any effect with a pre-specified type I error rate and power. Assuming that a time to event follows an exponential distribution, we describe the relationships between the effect size, the power, and the sample size. We present examples for illustration purposes. We provide a simulation study to verify the numerical calculations of the expected number of events and the duration of the trial. The change in the power produced by a reduced number of observations or by accruing no patients to certain factorial combinations is also described.
authors.affiliation: Biostatistics and Bioinformatics Department, Box 2717, Duke University Medical Center, Durham, NC 27710.
authors.forename: Barry Kurt
authors.initials: BK
authors.lastname: Moser
authors.affiliation: Biostatistics and Bioinformatics Department, Box 2717, Duke University Medical Center, Durham, NC 27710.
authors.forename: Susan
authors.initials: S
authors.lastname: Halabi