Abstract #301364

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JSM 2003 Abstract #301364
Activity Number: 420
Type: Contributed
Date/Time: Wednesday, August 6, 2003 : 2:00 PM to 3:50 PM
Sponsor: Section on Statistics in Epidemiology
Abstract - #301364
Title: Heterogeneity Effect Analysis of Bladder Cancer Data Using Frailty Model
Author(s): Jeffrey R. Wilson*+ and Xiaoli Hu
Companies: Arizona State University and Arizona State University
Address: PO Box 873806, Tempe, AZ, 85287-3806,
Keywords: frailty ; overdispersion ; Weibull
Abstract:

Frailty models were used to analyze the heterogeneity effects in bladder cancer data. All patients had superficial bladder tumors on entering the trial. Tumors were removed transurethrally and patients were randomly assigned to one of three treatment groups: placebo, thiotepa, and pyridoxine. Patients had multiple recurrences during the study, and new tumors were removed at each visit. The first four recurrence times were modeled consisting of the placebo group and the thiotepa group. Wei et al. (1989) used these data to do regression analysis through the marginal distributions. However, no frailty analysis of these data has been done. The likelihood ratio test for frailty is significant for Weibull specification, but insignificant for lognormal model. The likelihood ratio test for frailty indicates that there are group effects for Weibull model, but not for the lognormal model. Residual plots to check the goodness of fit of Weibull model and lognormal model showed that Weibull model fit the data better than lognormal model. Hazard functions under the frailty models were obtained.

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