NTP has gathered 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, we maintain a historical summary of the observations made on the untreated or control groups from individual studies as follows:
- Tumor incidences and growth and survival curves for control animals from NTP's two-year carcinogenesis studies are summarized by species, sex, route of administration, and vehicle.
- The data for control animals fed the NTP-2000 Diet are periodically updated and compiled from the most recent five-year period of results.
- The data for control animals fed the NIH-07 Diet were compiled from the most recent studies (usually a five-year period) through 1995, when NTP switched to the NTP-2000 diet.
Note: The historical controls data for genetically modified models are displayed separately.
Learn the history of rat models used by NTP
Commentary: Update on Animal Models for NTP Studies contains a thorough discussion on rat strain selection considerations. The following history summarizes part of the discussion.
For more than 30 years, NTP used the inbred F344/N rat for toxicity and carcinogenicity studies. Over time, this substrain developed decreased fecundity, sporadic seizures, and idiopathic chylothorax. The F344/N possessed other health issues inherent to the strain including high rates of mononuclear cell leukemia and testicular neoplasia.
In 2005, NTP held the NTP Workshop: Animal Models for the NTP Rodent Cancer Bioassay: Stocks and Strains – Should we Switch?. Workshop participants recommended three options to NTP:
- Establish another colony of the F344 rat from another source,
- use an F1 hybrid, or
- use an outbred stock of rat such as the Wistar Han or the Sprague Dawley.
NTP initially switched to the F344/NTac rat. This temporary change enabled NTP time to continue planned studies while exploring other rat models. NTP determined that a common default rat model to be used across study types would be useful.
NTP selected the Wistar Han rat as the default model as it was projected to have a long life span, resistance to disease, large litter size, and low neonatal mortality. However, in several studies with perinatal exposure, the average litter sizes were smaller than expected, the litters had a high variability in sex distribution, and pregnancy rates in time mated Wistar Han rats were not acceptable.
Consequently, NTP adopted the Harlan Sprague Dawley rat as the default NTP rat strain. NTP's decision came after much deliberation including consideration of historical data from eight previous NTP cancer studies using the female Sprague Dawley rat, and very favorable data on litter size, sex ratio, and body weight.
Tables and Curves
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 database 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 summary of tumor incidence in control animals is updated annually or semi-annually depending on the number of studies completed.
Table of Historical Controls
How to search with filtering and sorting
Search for particular tables by filtering or sorting the table. As you begin to type your search entry, the page will filter the table results by text. For example, type "F344" to see Fischer F344/N Rats rows.
To sort the table by a specific column, click the up/down filter arrow in the table header for that column. When clicked, the column headers will sort the table by ascending or descending order. If only one arrow is displayed, that column is sorted in the direction of the arrow. To sort more than one column, click the first column header, and then hold the shift key and click on additional column headers.