The incidence of bladder and
liver neoplasms developed in mice continuously fed
2-acetylaminofluorene (2-AAF) in a multidisciplined study conducted at the National Center for Toxicological Research (NCTR) is represented using a probit model. The estimated incidences are made from time intervals using both sacrificed and dead and moribund mice. A probit log dose model is fit for each type of
neoplasm at each time interval where the incidence permits. A probit log time model is fit for each of the neoplastic types for each dose level where the incidence permits. Finally, the response of
liver neoplasms to
2-AAF is represented in the dose time plane using a probit plane model.
2-AAF appears to be an early acting bladder
carcinogen and a late acting liver
carcinogen. The bladders seem to be much more uniform in their response to the
carcinogen than the livers and the uniformity of neither response appears to be age dependent. Although the time to appearence of both liver and
bladder neoplasms is dose related, the increment in incidence of
liver neoplasms with respect to time is not dose related while that of the
bladder neoplasms is dose related. The data for
bladder neoplasms do not contradict the "no threshold" theory of
carcinogenesis while the liver data strongly support it.