title: Menopausal oestrogens and breast cancer risk: an expanded case-control study.
abstract: A study among 1960 post-menopausal breast cancer cases and 2258 controls identified through a nation-wide screening program enabled evaluation of effects of oestrogen use on breast cancer risk. Ever use was not associated with increased risk (RR = 1.0), but a significant trend was observed with increasing years of use, with users of 20 or more years being at a 50% excess risk. Elevations associated with long-term use were apparent across all menopause subgroups (natural, ovaries retained, ovaries removed). Hormones exerted particularly adverse effects in those initiating use subsequent to a diagnosis of benign breast disease, particularly long-term users (RR = 3.0, 95% CI 1.6-5.5). There was also some indication that effects predominated among the lower stage tumours, an observation similar to that observed for endometrial cancer. These findings support a role for oestrogens in the aetiology of breast cancer, although risk appears to be enhanced only after extended periods of use, and not to the extent observed for other hormonally-sensitive tumours.
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000139:chemically induced*; D004967:Estrogens / Q000008:administration & dosage / Q000009:adverse effects*; D005260:Female; D006801:Humans; D008593:Menopause; D008875:Middle Aged; D012306:Risk; D013997:Time Factors
chemical_list: D004967:Estrogens