Phytoestrogens and breast cancer in postmenopausal women: a case control study

Objective: To examine the association between isoflavones, androgens, and d ietary composition and the risk of breast cancer in Australian postmenopaus al women. Design: Eighteen women with recently diagnosed breast cancer before surgery and 20 controls were recruited over a 12-month period. Both cases and cont rols were similarly assessed for urinary isoflavones, serum and urinary sex steroids, and dietary intake. Results: Women with breast cancer had lower 24-h urinary daidzein compared with controls (cases: 31 [95% CI: 4, 234] nmol/day; controls: 427 [95% CI: 4, 234] nmol/day; p = 0.03), and there was a trend to lower urinary geniste in excretion (cases: 25 [95% CI: 5, 132] nmol/day; controls: 155 [95% CI: 4 3, 550] nmol/day; p = 0.08). Total testosterone was higher in women with br east cancer compared with controls (cases: 1.3 [95% CI: 1.1, 1.5] nmol/L; c ontrols: 1.0 [95% CI: 0.8, 1.1] nmol/L; p = 0.05). No significant differenc es were found for serum sex hormone binding globulin, free androgen index, dehydroepiandrosterone sulphate, estradiol and progesterone, or in urinary androgen metabolites, or in dietary intake with regard to fat, carbohydrate , protein, or fiber consumption between cases and controls. Conclusions: This preliminary study is the first report of low urinary daid zein and genistein in postmenopausal women with breast cancer. These findin gs are in keeping with the increasing observational data demonstrating a pr otective effect from phytoestrogens on breast cancer risk. (Menopause 2000, 7:289-296, (C) 2000, The North American Menopause Society.).