TABLE B3. ANALYSIS OF PRIMARY TUMORS IN FEMALE RATS IN THE TWO-YEAR FEED STUDY 



OF NITROFURANTOIN (Continued) 



(a) Number of tumor-bearing animals/number of animals examined at the site 



(b) A malignant pheochromocytoma was observed in an animal with a benign pheochromocytoma. 



(c) Kaplan-Meier estimated tumor incidences at the end of the study after adjusting for intercurrent mortality 



(d) Observed tumor incidence at terminal kill 



(e) Beneath the control incidence are the P values associated with the trend test. Beneath the dosed group incidence are the 

 P values corresponding to pairwise comparisons between that dosed group and the controls. The life table analysis regards tu- 

 mors in animals dying prior to terminal kill as being (directly or indirectly) the cause of death. The logistic regression test re- 

 gards these lesions as nonfatal. The Cochran-Armitage and Fisher exact tests compare directly the overall incidence rates. 

 A negative trend or lower incidence in a dosed group is indicated by ( N ). 



Nitrofurantoin, NTP TR 341 



128 



