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Biostatistics Advance Access published online on April 28, 2005
Biostatistics, doi:10.1093/biostatistics/kxi030
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© The Author 2005. Published by Oxford University Press. All rights reserved. For permissions, please e-mail: journals.permissions@oupjournals.org.
Received December 16, 2004
Revised April 21, 2005
Accepted April 26, 2005

Article

Robust modeling in Screening Studies: Estimation of Sensitivity and Pre-clinical Sojourn Time Distribution

Yu Shen 1* and Marvin Zelen 2

1 Department of Biostatistics and Applied Mathematics, M. D. Anderson Cancer Center, University of Texas, Houston, Texas 77030, USA
2 Department of Biostatistics, Harvard School of Public Health and the Dana-Farber Cancer Institute, Boston, Massachusetts 02115, USA

* To whom correspondence should be addressed.
Yu Shen, E-mail: yshen{at}mdanderson.org


  Abstract

In early detection clinical trials, quantities such as the sensitivity of the screening modality and the pre-clinical duration of the disease are important to describe the natural history of the disease and its interaction with a screening program. Assume the schedule of a screening program is periodic and that the sojourn time in the pre-clinical state has a piecewise density function. Modeling the pre-clinical sojourn time distribution as a piecewise density function results in robust estimation of the distribution function. Our aim is to estimate the piecewise density function and the examination sensitivity using both generalized least squares and maximum likelihood methods. We carried out extensive simulations to evaluate the performance of the methods of estimation. The different estimation methods provide complimentary tools to obtain the unknown parameters. The methods are applied to three breast cancer early detection trials.

Keywords: Piecewise-constant density function; Preclinical duration; Screening clinical trials; Screening sensitivity; Weighted least squares.
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