Abstract #300620

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JSM 2003 Abstract #300620
Activity Number: 31
Type: Contributed
Date/Time: Sunday, August 3, 2003 : 2:00 PM to 3:50 PM
Sponsor: Biopharmaceutical Section
Abstract - #300620
Title: Calculation of Sample Size in Survival Trials: The Impact of Informative Noncompliance
Author(s): Qi Jiang*+ and Steven M. Snapinn and Boris Iglewicz
Companies: Merck Research Laboratories and Merck & Co., Inc. and Temple University
Address: 10 Woodstone Dr., Doylestown, PA, 18901-7011,
Keywords: censored observations ; exponential distribution ; survival analysis ; modified Lakatos method
Abstract:

Sample size calculations for survival trials typically include an adjustment to account for the expected degree of noncompliance with the study medications. Existing sample size methods assume that when patients discontinue study medications, they do so independently of their risk of an endpoint; that is, that noncompliance is noninformative. However, this assumption is not always true, as we illustrate using results from three clinical trial databases. We introduce a modified version of the method proposed by Lakatos (1988) that can be used to calculate sample size under informative noncompliance. This method is based on the concept of two subpopulations, one with high rates of endpoint and discontinuation, and another with low rates. Using this new method, which we validate by simulation, we show that failure to consider the impact of informative noncompliance can lead to a considerably underpowered study.

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