Abstract #300885


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JSM 2002 Abstract #300885
Activity Number: 317
Type: Contributed
Date/Time: Wednesday, August 14, 2002 : 10:30 AM to 12:20 PM
Sponsor: Biometrics Section*
Abstract - #300885
Title: Extending the Survival-adjusted Cochran-Armitage Test by Estimating k for the Poly-k Test
Author(s): Hojin Moon*+ and Hongshik Ahn and J. Lee and Ralph Kodell
Affiliation(s): U. T. M. D. Anderson Cancer Center and State University of New York, Stony Brook and U. T. M. D. Anderson Cancer Center and National Center for Toxicological Research
Address: 1515 Holcombe Blvd., - 447, Houston, Texas, 77030-4009, U.S.A
Keywords: Bioassay ; Dose-response ; Multiple-sacrifice animal carcinogenicity studies ; Trend test ; Tumor incidence rate
Abstract:

This study extends the survival-adjusted Cochran-Armitage test in order to achieve improved robustness to a variety of tumor onset distributions. The Cochran-Armitage test is routinely applied for detecting a linear trend in the incidence of a tumor across dose groups. To improve the robustness to the effects of differential mortality across groups, Bailer and Portier (1988, Biometrics, 44, 417-431) introduced the Poly-3 test by a survival adjustment, using a fractional weighting scheme for subjects not at full risk of tumor development. They further suggested that this test could be improved by using a general k reflecting the shape of the tumor onset distribution. We propose a method to estimate k by equating the empirical lifetime tumor incidence rate obtained from the data to a separately-estimated cumulative lifetime tumor incidence rate. The proposed method performs better than the Poly-3 test conducted without prior knowledge of the tumor onset distribution. The robustness of the proposed test to various tumor onset distributions and the consistency of the proposed method are shown in simulation studies. The proposed method is also illustrated in analyzing a real data set.


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