A RASH ANALYSIS OF NATIONAL TOXICOLOGY PROGRAM DATA - PREDICTIONS FOR30 COMPOUNDS TO BE TESTED IN RODENT CARCINOGENESIS EXPERIMENTS

Relative potencies for 30 compounds scheduled for carcinogenic testing in the 2-year rodent bioassays were estimated based on comparisons wi th a wide variety of bioassay data for benzo[a]pyrene, nicotine, cispl atin, aflatoxin B-1, and cyclophosphamide. Potential for oncogenic tra nsformation of each of the compounds was estimated from short-term bio assays. Promoting strength was assigned on the basis of comparisons of the product of relative potency and test dose with the distribution o f similar products obtained for 67 common compounds in the database of Gold et al. A potency class for promotion was assigned on the basis o f whether the potency-adjusted test dosage was > 2 sigma below the mea n, > 1 sigma below the mean, within +/-sigma of the mean, > sigma abov e the mean, or > 2 sigma above the mean, as determined from the 67 com pounds. The underlying hypothesis is that a weak test dose may have a low probability of revealing a potential carcinogen, whereas a strong dose may have a high probability of producing false-positive results. Predictions are therefore directed at the central 68% of the log-norma l frequency distribution according to the assumption that +/-sigma rep resents the ideal test dose.