Oestrogens and Breast Cancer: Present Position

Oestrogen is probably involved in breast cancer in two main ways: (1) in the aetiology of the disease as a promoting substance rather than as a carcinogen; (2) in stimulating the growth of at least some established breast cancers, acting through the oestrogen receptor. Successful modes of endocrine therapy would then be interpreted as interfering with (a) the supply of oestrogen to the tumour (b) the nuclear events in oestrogen action or (c) receptor replenishment.Estrogens can be involved in breast cancer in the following 2 ways: 1) as a promoting rather than a carcinogenic agent in the formation of breast cancers; and 2) as a stimulant to the growth of established breast tumors through the estrogen receptor. The evidence linking estrogen with the etiology of breast cancer is, however, largely circumstantial. Successful endocrine therapy would interfere with the supply of estrogen to the tumor, the nuclear events in estrogen action, or receptor replenishment. The minimal criterion for therapeutic success with endogenous estrogen therapy is to effect a reduction in hormone levels. Only tumors with endocrine sensitivity, indicating the presence of estrogen receptors, will respond, it is believed. The absence of estrogen receptors predicts failure for this type of therapy. Studies have shown that the estrogenic components of OCs (oral contraceptives) do not lead to an increased risk of breast cancer except perhaps in a small subgroup of women already at high risk.