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Abstract Details

Activity Number: 616
Type: Contributed
Date/Time: Thursday, August 2, 2012 : 8:30 AM to 10:20 AM
Sponsor: Biopharmaceutical Section
Abstract - #304784
Title: A Group Sequential Method Based on the Weighted Log-Rank Test for Delayed Treatment Effects
Author(s): Mizuki Yoshida*+ and Yutaka Matsuyama
Companies: Pfizer Inc. and University of Tokyo
Address: 3-22-7, Yoyogi, Shibuya-Ku, Tokyo, _, 151-8589, Japan
Keywords: alpha-spending function ; delayed treatment effect ; interim analysis ; dependent increments ; weight-adjusted log-rank test
Abstract:

Fleming and Harrington's Gp,r class of weighted log-rank tests is appropriate for detecting delayed treatment effects such as seen in cancer vaccines. When the interim analyses with the aim of early termination due to efficacy are conducted, an alpha-spending function method (ASFM) is useful. However, the ASFM assumes the independent increments of test statistics. Therefore, a type I error increases from the nominal level if an ASFM is applied for the weighted log-rank test statistic under the staggered patient entry. In this talk, we perform the quantitative evaluation of the degree to which a type I error is inflated. It was demonstrated that a type I error increased very little under the moderate situation, and it is of no matter from a practical standpoint. Next, we propose the weight-adjusted log-rank test statistic to control an overall type I error exactly at the desired level. We further consider the problems of estimating hazard functions accounting for delayed effects and discuss the estimation of parameters for the change point models. The proposed method will provide a valuable tool for adjustment of multiplicity.


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