Abstract #300320

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JSM 2003 Abstract #300320
Activity Number: 30
Type: Contributed
Date/Time: Sunday, August 3, 2003 : 2:00 PM to 3:50 PM
Sponsor: Biometrics Section
Abstract - #300320
Title: Evaluating a Group Sequential Design in the Setting of Nonproportional Hazards
Author(s): Daniel L. Gillen*+ and Scott S. Emerson
Companies: University of Washington and University of Washington
Address: 1705 NE Pacific-Box 357-232, Seattle, WA, 98195-7232,
Keywords: censored data ; clinical trials ; nonparametric statistics ; nonproportional hazards ; sequential tests
Abstract:

Group sequential methods have been widely described and implemented in the clinical trial setting when parametric and semiparametric models are deemed appropriate. In these situations, the evaluation of stopping rules used for the planning and design of clinical trials remains relatively straightforward. However, when nonparametric methods are used, as is often the case for nonproportional hazards survival data, the evaluation of stopping rules is not a trivial task. Specifically, nonparametric test statistics do not necessarily correspond to a parameter of interest, making it difficult to characterize alternatives at which operating characteristics are to be computed, and sometimes leading to contradictions when reporting clinically meaningful measures of treatment effect that do not correspond to the nonparametric statistic for which testing is based upon. We propose methods for the construction of alternatives under nonproportional hazards using pre-existing pilot data. Case studies using these methods are presented to evaluate the operating characteristics of selected group sequential designs when testing is based upon nonparametric weighted logrank statistics.

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