EXTINCTION OF EXPERIMENTAL MAMMARY CANCER, I. ESTRADIOL-17β AND PROGESTERONE

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Abstract
A single feeding of 7,12-dimethylbenz(a)anthracene to rats induced mammary cancer. Hormone modifications which induced exuberant growth of normal mammary glands were furnished for a limited time in groups of animals which had been fed this hydrocarbon 15 days earlier. Pregnancy accelerated the growth of mammary cancers. Progesterone, alone, had a similar cancer-promoting effect in intact females. Estradiol-17[beta] delayed the appearance of cancer of the breast, and eventually 100% of the animals developed mammary cancer. Estradiol- 17[beta] administered concurrently with progesterone destroyed a significant number of mammary cancers; 52% of the rats treated with this combination of hormones apparently were free from cancer after six months. This is the extinction of cancer through hormone-interference with a steroid mechanism which is essential for the life of the malignant cell. Estradiol-17[beta] with progesterone induced extensive hyperplasia of normal mammary glands and did not destroy benign tumors of the breast or cancer of the ear duct. The combined administration of estradiol- 17[beta] and progesterone was not toxic, nor did it cause a long-continued depression of activity of the ovaries; normal ovarian function was restored promptly after cessation of 30-day hormone treatment.