Abstract #302337

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JSM 2003 Abstract #302337
Activity Number: 133
Type: Contributed
Date/Time: Monday, August 4, 2003 : 12:00 PM to 1:50 PM
Sponsor: Biometrics Section
Abstract - #302337
Title: A Test for Trend and Its Application in Photocarcinogenicity Experiments
Author(s): Daniel F. Molefe*+
Companies: National Center for Toxicological Research
Address: 3900 NCTR Rd., Jefferson, AR, 72079-9501,
Keywords: dose response ; k-groups ; likelihood ratio ; Monte Carlo simulation
Abstract:

Photocarcinogenicity experiments are designed to study the effects of simulated solar light in conjunction with the topical application of a test agent on the skin of SKH-1 mice. The rodents receive increasing doses of a test agent combined with increasing doses of simulated solar light over a period of 40 weeks followed by a 12-week period of no treatment. Each week, the number of observed tumors and the times to observation (latency) of tumors exceeding a prespecified size (e.g., 5 millimeter) are recorded. To establish if the dose has an effect on the number of induced tumors (frequency) and/or on the latency of tumors, we propose a frequency-latency trend (FLT) test. The test, which is implemented using a FORTRAN 90 program, is applied to real data from the National Center for Toxicological Research (NCTR). It is shown through Monte Carlo studies that the proposed test can detect overall group differences in the number of observed tumors as well as isolate whether this overall difference is due to differences in frequency and/or latency. The simulation study also compares the size and power of the FLT test compared to Tarone's test for trend effect (Tarone, 1975).

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