The NTP has amassed a significant database of results collected on toxicity studies. To follow changes in the biology of our test species and also as an additional way to evaluate test results, an historical summary of the observations made on the untreated or control groups from individual studies is maintained.
Tumor incidences and growth and survival curves for control animals from the NTP's two-year carcinogenesis studies are summarized by species, sex, route of administration, and vehicle. The historical controls for the genetically modified models are also separated.
The data represent two rodent species: Fischer 344/N rats and B6C3F1 mice.
The data for control animals fed the NIH-07 Diet were compiled from the most recent studies (usually a 5-year period) through 1995, when NTP switched to the NTP-2000 diet.
In the pathology tables, tumor incidence is defined as the number of animals exhibiting a particular tumor type divided by the number of animals examined and is expressed as both raw counts and percent. The pathology tables present the mean, standard deviation, and range of tumor incidence among studies, along with the number of studies summarized and the date when the historical data base was most recently updated.
The growth curves present the mean growth for each route/species/sex group of control animals along with the 5th and 95th percentile.
The survival curves present the mean survival for each route/species/sex group of control animals along with the 5th and 95th percentile.
The historical data from which these tables and curves for control animals were extracted are maintained in the NTP Toxicology Data Management System (TDMSE) at NIEHS. The summary of tumor incidence in control animals is updated annually or semi-annually depending on the number of studies completed.