Sex hormone levels in the blood are not associated with the risk of developing breast cancer in postmenopausal women who are in high-risk groups, according to a new study.
Several studies have suggested that increased levels of the sex hormones estradiol and testosterone and decreased levels of a protein that binds to sex hormones called sex hormone-binding globulin are associated with an increased risk of breast cancer in postmenopausal women. Although tamoxifen is commonly used to treat breast cancer in postmenopausal women, one study suggested that raloxifene, a selective estrogen receptor modulator (SERM), was associated with a larger reduction in breast cancer risk among women with high levels of estradiol.
Mary S. Beattie, M.D., of the University of California in San Francisco, and colleagues examined the levels of sex hormones estradiol and testosterone, and sex hormone-binding globulin in the blood plasma of 135 postmenopausal women with breast cancer and 275 postmenopausal control women who had been treated with tamoxifen or placebo as part of a breast cancer prevention trial. The authors sought to determine whether sex hormone levels are associated with breast cancer risk, and whether breast cancer risk reduction varied by sex hormone level among women on tamoxifen, which is also a SERM.
Their results showed that levels of sex hormones were not associated with breast cancer risk in these women and cannot be used as a predictor for breast cancer risk or determine who would most benefit from tamoxifen treatment. Tamoxifen had the same effect on breast cancer risk in women with high and low levels of estradiol. The authors suggest that the study should be repeated in other populations with a high risk of developing breast cancer.
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Journal of the National Cancer Institute
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