Data quality in predictive toxicology: Reproducibility of rodent carcinogenicity experiments

We compared 121 replicate rodent carcinogenicity assays from the two parts (National Cancer Institute/National Toxicology Program and literature) of t he Carcinogenic Potency Database (CPDB) to estimate the reliability of thes e experiments. We estimated a concordance of 57% between the overall rodent carcinogenicity classifications from both sources. This value did not impr ove substantially when additional biologic information (species, sex, strai n, target organs) was considered. These results indicate that rodent carcin ogenicity assays are much less reproducible than previously expected, an ef fect that should be considered in the development of structure-activity rel ationship models and the risk assessment process.