An Empirical Comparison of Methods Used to Estimate Carcinogenic Potency in Long-Term Animal Bioassays: Lifetable vs Summary Incidence Data

An Empirical Comparison of Methods Used to Estimate CarcinogenicPotency in Long-Term Animal Bioassays: Lifetable vs SummaryIncidence Data. GOLD, L. S., BERNSTEIN, L., KALDOR, J., BACKMAN,G., AND HOEL, D. (1986). Fundam. Appl. Toxicol. 6, 263–269.Two methods forestimating carcinogenic potency from animal carcinogenesisbioassays (TD50-defined in the paper) are compared, one basedon lifetable data and one based on summary incidence data. Thelifetable analysis adjusts for the differential effects of toxicityamong dose groups and for differences in the time pattern oftumor incidence, while summary incidence analysis does not.However, summary data are all that are usually available inthe published results of animal cancer tests. Using NCI bioassayresults which provide full lifetable data, we compare lifetableand summary estimates of potency and their statistical significanceas well as the estimated shape of the dose—response curve.There is substantial agreement between these methods of analysisin terms of potency estimation, although lifetable estimatesare usually more potent. But there are some notable differencesin the estimated shape of the dose—response curve, suggestingthat both target site selection and method of analysis playan important role in risk estimation.