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Excess mortality in two-year rodent carcinogenicity studies.
A Roth1, E Kadyszewski, B Geffray
1Department of Statistics Pfizer Global Research and Development, Groton, CT, USA.
Toxicologic Pathology
|December 22, 2007
Summary
This study suggests optimizing rodent carcinogenicity study designs by adjusting doses or terminating studies early to improve cancer risk assessment. It also proposes new statistical methods for analyzing mortality data and recommends regulatory agency consultation.
Area of Science:
- Toxicology
- Carcinogenesis Research
- Biostatistics
Background:
- Differential mortality complicates interpretation of 2-year rodent carcinogenicity studies.
- Current experimental designs may not fully leverage data when excess mortality occurs.
Purpose of the Study:
- To provide recommendations for experimental design and statistical analysis of rodent carcinogenicity studies experiencing differential mortality.
- To enhance the utility of these studies for carcinogenic risk assessment.
Main Methods:
- Reviewing impacts of various mortality patterns on study interpretation.
- Proposing dose reduction strategies, including dose cessation.
- Suggesting study termination as an alternative to terminating specific dose groups.
- Recommending modifications to statistical analysis, including a new test for maximum tolerated dose (MTD).
Main Results:
- Adjusting experimental design (e.g., dose reduction, study termination) can improve data value.
- Modified statistical analyses are necessary to accommodate design changes.
- A new statistical test for MTD based on mortality is proposed.
Conclusions:
- Implementing proposed design and analysis modifications can enhance carcinogenic risk assessment.
- Early engagement with regulatory agencies (e.g., FDA) is crucial for implementing these changes.
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