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Title: Sex hormone levels and risks of estrogen receptor-negative and estrogen receptor-positive breast cancers
Authors: Farhat, Ghada N.
Cummings, Steven R.
Chlebowski, Rowan T.
Parimi, Neeta
Cauley, Jane A
Rohan, Thomas E.
Huang, Alison J.
Vitolins, Mara
Hubbell, F. Allan
Affiliations: Department of Public Health 
Keywords: Testosterone
Gonadal steroid hormones
Testosterone measurement
Estrogen receptor negative
Breast cancer risk
Subjects: Cancer
Breast cancer
Issue Date: 2011
Part of: Journal of the national cancer institute
Volume: 103
Issue: 7
Start page: 562
End page: 570
Background Endogenous sex hormone levels are associated with risks of breast cancer overall and estrogen receptor (ER)–positive breast tumors; however, their associations with ER-negative tumors remain unclear. Methods In a case–cohort study within the Womens Health Initiative Observational Study among postmenopausal women aged 50–79 years, we examined associations between endogenous testosterone and estradiol levels and the risks of ER-negative and ER-positive breast cancers. Serum levels of bioavailable testosterone and estradiol were assessed at the baseline visit in 317 invasive breast cancer case subjects and in a subcohort of 594 women. Bioavailable sex hormone levels were calculated using the total hormone level and the sex hormone–binding globulin concentration (measured by radioimmunoassays and a chemiluminescent immunoassay, respectively). Cox proportional hazards regression was used for statistical analysis. All statistical tests were two-sided. Result The unadjusted absolute rates of ER-negative breast cancer for testosterone quartiles 1–4 were 0.34, 0.20, 0.23, and 0.21 per 10 000 person-years, respectively. Compared with women in the lowest quartile of testosterone level, those in quartile 2 had a 56% lower risk of ER-negative cancer (hazard ratio [HR] = 0.44, 95% confidence interval [CI] = 0.23 to 0.85), those in quartile 3 had a 45% lower risk (HR = 0.55, 95% CI = 0.30 to 1.01), and those in quartile 4 had a 49% lower risk (HR = 0.51, 95% CI = 0.28 to 0.94), independent of other risk factors. Estradiol level was not associated with ER-negative breast cancer. ER-positive breast cancer risk increased with higher testosterone levels ( Ptrend = .04), but this trend was not statistically significant after adjustment for estradiol ( Ptrend = .15). ER-positive cancer risk was approximately twofold higher in women with estradiol levels in quartiles 2–4 compared with women in quartile 1, independent of risk factors. Conclusion Higher serum level.
DOI: 10.1093/jnci/djr031
Ezproxy URL: Link to full text
Type: Journal Article
Appears in Collections:Department of Public Health

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