Pre- and postmenopausal breast cancer

Abstract

It has been postulated that breast cancer is not a single disease, and that the risk factors occurring in premenopausal women are different from those occurring in postmenopausal women. This case-control study of pre- and postmenopausal breast cancer was designed to investigate a variety of variables including age of menarche, parity, age at first full-term birth, breast feeding patterns, age at menopause, and history of oral contraceptive use. The study compared 60 breast cancer cases and 125 matched controls from the same breast cancer screening population. Cases and controls were matched for race, age, place of birth, marital status, education, and annual family income. More cases than controls used oral contraceptives; the differences were statistically significant. The risk ratio estimates were 2.9 (confidence intervals 1.19-7.15). The mean duration of oral contraceptive use was more than two times longer among premenopausal breast cancer cases than controls and five times longer among postmenopausal cases than the controls. The breast cancer cases had significantly more relatives with a history of other cancers than the control group (risk ratio estimate 2.3, P < 0.03). No association was found between height and breast cancer; however, cases were found to be significantly heavier than controls. No differences were found in reproductive variables between breast cancer patients and their matched controls. In addition, a subdivision of breast cancer cases into pre- and postmenopausal groups did not reveal any clear differences in reproductive variables that would support the hypothesis that different specific risk factors are operating during pre- and postmenopausal periods.