Effects of an androgenic derivative on the development of chemically-induced mammary carcinogenesis in the rat.

The effects of an androgenic derivative--danazol--on the development of dimethylbenz(a)anthracene (DMBA)-rat mammary carcinogenesis were studied. Animals in the treated group received danazol (10-12 mg/kg/day) during 169 days, starting 5 days after DMBA induction. As compared with tumours in control animals, those treated with danazol appear later and are significantly smaller. Moreover, this treatment reduced the incidence of animals affected by mammary cancer and the average number of malignant tumours in each animal. In the same way, the incidence of animals with missing nodules was significantly higher in the group treated with danazol. It is concluded that danazol has an inhibitory effect on experimental mammary tumours. This effect seems to be greater the earlier the treatment is started and the longer time it is applied.