Therapy of dimethylbenzanthracene-induced mammary carcinomas in the rat by selective inhibition of steroidogenesis.

The effects of cyanoketone, a specific inhibitor of steroidogenesis at the levels of 3beta-hydroxysteroid oxidoreductase-dealta54-3-ketosteroid isomerase, the combination of cyanoketone with corticosterone, and corticosterone alone on the growth of dimethylbenzanthracene-induced hormone-dependent breast cancers in rats were compared with that produced by ovariectomy. Cyanoketone produces about as many regresssions of these cancers as does ovariectomy. However, cyanoketone with corticosterone results in a significant regression of tumors in all animals tested. This therapy also causes regression of significantly more tumors that are large at the beginning of treatment than does ovariectomy. These findings suggest that this kind of reversible blockade of steroidogenesis may be useful as a diagnostic tool in assessing the hormone dependence of breast tumors and as a possible therapeutic approach in the treatment of such tumors.