Table 2

Therapeutic effect of intraductally administered 5-FU on MNU-induced rat mammary tumors. Two weeks after MNU injection, when hyperplasias, MINs, and microscopic carcinomas—but no palpable lesions—were present in the mammary glands, rats were treated with the indicated agent. Eleven rats received 5-FU injected intraductally into 4 mammary glands (second to the fifth) each (n = 44 mammary glands total), whereas the remaining 8 mammary glands in each animal received no treatment (n = 88 total; labeled as “uninjected”). Ten rats received 5-FU intravenously (120 mammary glands total) and 20 rats remained untreated (240 mammary glands total). Rats were killed at 22 weeks after the initiation of treatment. Time to emergence of tumors was analyzed with the individual gland as the analysis unit with Cox proportional hazards model, where correlations between observations within the same cluster (rat) were taken into account. Multiple comparisons were adjusted with the Bonferroni procedure. id, intraductal; iv, intravenous.

Treatment comparisonNumber of tumors at the end of the study/number of glandsHazard ratio95% CIP
No treatment versus 5-FU id injected103/240 versus 7/443.301.50–7.250.018
5-FU iv versus 5-FU id injected59/120 versus 7/444.021.73–9.360.006
5-FU iv versus 5-FU id uninjected59/120 versus 25/882.061.19–3.550.054
No treatment versus 5-FU id uninjected103/240 versus 25/881.691.08–2.640.126
5-FU id uninjected versus 5-FU id injected25/88 versus 7/441.950.88–4.360.612
No treatment versus 5-FU iv103/240 versus 59/1200.820.55–1.22>0.999