Biologic characteristics and chemotherapy of 7,12-dimethylbenz[a]anthracene-induced tumors in rats.

The biologic characteristics and susceptibility to steroid ther apy were determined for multiple mammary tumors induced in Sprague-Dawley rats by single intragastric doses of DM HA.3 Tumors were produced in 70-78% of 1016 rats within 120 days of administration of 15, 20, or 30 mg of DMBA. Mortality was 20% in rats given the highest dose. Only 52-63% of the rats had tumors usable for experimental chemotherapy. In 20 representa tive rats, 86 mammary tumors comprised 97.6% of all masses removed at autopsy, 92% of which were malignant. Growth be havior of tumors was unpredictable, a variable number growing, regressing, or remaining static in the same host. Bilateral ovariectomy on 70 rats produced tumor regression in 57%• These re mained tumor free from 11 to less than 35 weeks. Steroids pro ducing complete remission of all tumors in 40% or more of the treated rats were: 5a-androstan-3a,17;3-diol dipropionate; 2amethyldihydrotestosterone; its propionate, testosterone propi onate; 9a-fluoro-ll/3-hydroxy-17-methyltestosterone; and 6/3methyldihydrotestosterone propionate. 1-Dehydrotestololactone was relatively inactive. Preliminary tests with nonsteroids yielded inconclusive results because of high toxicity.