The two anthracycline antitumor antibiotics, Adriamycin and daunomycin (DM), induced a high incidence of mammary tumors, both fibroadenomas and adenocarcinomas, in female rats that received a single i.v. dose, thus confirming previous results. The incidence of DM-induced adenocarcinomas increased with the dose of the drug, whereas the incidence of Adriamycin-induced adenocarcinomas showed a plateau at 5 mg/kg and above. Adriamycin- and DM-induced fibroadenomas showed a peak at lower doses

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... 5 to 6 mg/kg). With the highest DM dose (12.5 mg/kg) used, there was a slight prevalence of adenocarcinomas over fibroadenomas.