Statistical Methods for Estimating LTD₁₀ from TD₅₀ and Its Lower Confidence Limit

LTD₁₀ is the lower 95% confidence limit on the dose to induce tumors in 10% of animals. LTD₁₀ values are estimated from the CPDB using the TD₅₀ and 99% lower confidence limit as follows:

Both the TD₅₀ and the two-sided 99% confidence limits (LoConf, UpConf) are reported in the CPDB from fitting the one-hit model to experimental dose-response data using maximum likelihood methods. The one-hit model was selected because it is the most conservative of the multistage models. When both the TD₅₀ and the two-sided 99% confidence limits are available, it is shown in Gold et al. (2003) for the one-hit model that the lower 95% confidence limit for the TD₁₀, i.e., LTD₁₀ is:

This method gave similar estimates to the LTD₁₀ obtained by fitting the multistage model to the tumor incidence data for both linear and curved dose responses with high or low tumor rates in the controls and tight or wide confidence limits for the TD₅₀ (Gold et al., 2003). Thus, relatively precise estimates of the LTD₁₀ can be readily calculated from the TD₅₀ and LoConf from the CPDB.

LTD₁₀ values are reported in an Excel spreadsheet in each species for all chemicals in the CPDB with a positive evaluation of carcinogenicity by the author of at least one experiment.

See also Statistical Methods for Estimating TD₅₀.

References

• Gold, L.S., Gaylor, D.W., and Slone, T.H. Comparison of Cancer Risk Estimates Based on a Variety of Risk Assessment Methodologies. Regul. Toxicol. Pharmacol. 37: 45-53 (2003). PDF
• U.S. Environmental Protection Agency (2005). Guidelines for Carcinogen Risk Assessment. PDF

Return to the Carcinogenic Potency Database Project (CPDB) Home Page:

Last updated: August 6, 2007