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Experience, Expertise, Excellence |
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Long-Term Carcinogenicity Studies |
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The statistical analysis of data from toxicology often presents unique issues that are not common to other applications of statistics. A classic example is the statistical analysis of tumor findings from a long-term carcinogenicity (LTC) study.
Competing Factors Several factors associated with the LTC study complicate the statistical analysis of tumor findings. A simple comparison among treatment groups of the proportion of animals with a tumor may be biased by failure to take into account potentially competing factors.
Animals that live longer are more likely to develop tumors than those that die early.
The test compound may affect the survival rate of different treatment groups for reasons other than the tumor of interest (a competing risk).
Therefore, it is essential to incorporate an adjustment for survival rates in the statistical analysis of tumor findings.
Rate of Tumor Onset Ideally, the statistical analysis would be conducted on the rate of tumor onset among different treatment groups. However, determining a tumor’s time of onset is complicated by the limitations of tumor detection.
Other than tumors that can be detected by visual inspection or palpation (eg. skin, mammary), a tumor is only detected at necropsy. The actual time of tumor onset is unknown.
A simple comparison among treatment groups of the time of tumor detection is inadequate. There must be a distinction between a treatment which reduces survival due to shortened tumor latency (true carcinogenic effect) and one that also reduces survival but in which tumors are merely observed earlier due to death from some other competing risk (noncarcinogenic effect).
The BioSTAT Solution Governing regulatory agencies recognize the complications associated with the statistical analysis of tumor findings from LTC studies and have issued guidance documents addressing the issues. BioSTAT has the experience of providing statistical analysis, summary reports, and electronic submission datasets for the submission of numerous LTC studies. Call for more detail. |
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