Sex hormones and postmenopausal breast cancer: a prospective study in an adult community.

Few studies have examined the role of endogenous sex hormones in breast cancer, and to the authors' knowledge, only two have done so prospectively. The authors report here the results of a prospective study based on an available bank of previously analyzed plasma collected in 1972-1974 from 442 women aged 50-79 years in Rancho Bernardo, California. These women were followed for 12-15 years, during which time 42 cases of breast cancer were identified: 15 incident cases diagnosed 1 year or more after baseline, 18 prevalent cases diagnosed earlier than 1 year after baseline, and 9 cases with unknown dates of onset. No apparent trends in plasma levels of sex hormones or sex hormone-binding globulin and incidence or prevalence of breast cancer were observed. Mean crude and age-adjusted plasma hormone levels at baseline (in pg/ml) for incident cases, total cases, and noncases, respectively, were: androstenedione: 647, 638 +/- 328 (standard deviation); 626, 620 +/- 245; and 664, 664 +/- 291; testosterone: 254, 258 +/- 120; 238, 241 +/- 153; and 262, 261 +/- 143; estrone: 37, 38 +/- 18; 35, 35 +/- 15; and 37, 37 +/- 17, and estradiol: 13, 13 +/- 7; 15, 15 +/- 8; and 15, 15 +/- 9. For sex hormone-binding globulin, mean crude and age-adjusted levels at baseline (nM) were 35 and 36 +/- 33 for incident cases; 31 and 31 +/- 25 for total cases; and 29 and 29 +/- 21 for noncases. Cox proportional hazards multiple regression showed no associations with breast cancer after simultaneous adjustment for age, body mass index, and cigarette smoking.