Urinary phytoestrogen excretion and breast cancer risk: evaluating potential effect modifiers endogenous estrogens and anthropometrics.

Dai Q, Franke AA, Yu H, Shu XO, Jin F, Hebert JR, Custer LJ, Gao YT, Zheng W
Cancer Epidemiol Biomarkers Prev. 2003 12 (6): 497-502

PMID: 12814993

Steroid sex hormones play a central role in breast carcinogenesis. Evidence from in vitro and animal studies suggests that phytoestrogens may inhibit the development of mammary tumors through their role in regulating the synthesis, metabolism, and signal transduction of steroid hormones. In a study of 117 case-control pairs of postmenopausal women in Shanghai, we investigated whether the association between urinary phytoestrogen excretion and breast cancer risk may differ by levels of endogenous steroid sex hormones, sex hormone binding globulin (SHBG), body mass index (BMI), and waist:hip ratio (WHR). Fasting morning blood and urine samples were collected for the analysis of urinary isoflavonoids and mammalian lignans, as well as blood levels of SHBG and selected steroid hormones. For cancer patients, samples were collected before any cancer therapy. Conditional logistic regression models were used to estimate odds ratios and 95% confidence intervals after adjusting for potential confounding factors. The inverse associations between urinary phytoestrogens and breast cancer risk were found to be more evident among women with a high BMI or WHR than those with a low level of these anthropometric measurements. Although a reduced risk of breast cancer was observed among women with a high excretion rate of urinary isoflavonoids in all of the strata defined by blood SHBG and steroid hormones, the inverse association was more pronounced among women with a high blood concentration of estradiol, a low level of estrone sulfate, or a low level of SHBG. The risks of breast cancer were also reduced with increasing excretion rate of mammalian lignans, although no test for a linear association was statistically significant in stratified analyses. Findings from this study suggest that the potential protective association of phytoestrogens may be modified by BMI, WHR, and blood levels of SHBG, and steroid hormones.

MeSH Terms (25)

Adult Age Factors Anthropometry Biomarkers, Tumor Body Mass Index Body Weight Breast Neoplasms Case-Control Studies China Dehydroepiandrosterone Sulfate Eating Estrogens Female Fibroadenoma Humans Isoflavones Menopause Middle Aged Phytoestrogens Plant Preparations Risk Factors Sex Hormone-Binding Globulin Statistics as Topic Testosterone Women's Health

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