[Treatment of menopause and cancer of the breast: point of view of the hormonologist].

Whether or not postmenopausal estrogen-progestogen replacement therapy carries a risk breast cancer is a controversial subject. Very few epidemiological studies evaluate this risk since most of them, conducted in the United States, concern women treated with estrogens alone rather than combined with progestogens. The risk of breast cancer is high mainly when estrogens are used in high dose and for long periods in women with a past or present history of benign breast disease. The facilitating role played by oestrogens in the occurrence of benign, then cancerous breast diseases, is clear. Estrogens encourage cell multiplication and can stimulate the expression of certain oncogenes in cancerous lineages. The protective effect of progestogens against the risk of breast cancer is much more controverted. Progesterone tends to slow down the estrogen-induced cell multiplication and facilitates the terminal differentiation of galactophores into acini, the secretory structures. Two mechanisms have been characterized in normal mammary cells, mastopathies and hormone-dependent cancer cells: progesterone reduces the amount of oestradiol receptors and stimulates the activity of the 17-beta-hydroxysteroid dehydrogenase enzyme. In view of these data, it would be reasonable to give postmenopausal women oestrogens in low doses and always combined with progestogens. Every woman with risk factors for breast cancer, such as a family history of breast cancer or a long past of untreated benign breast disease, must be carefully evaluated.