Abstract | BACKGROUND: METHODS: In a case-cohort study within the Women's 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 (P(trend) = .04), but this trend was not statistically significant after adjustment for estradiol (P(trend) = .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 levels of bioavailable testosterone are associated with lower risks of ER-negative breast cancer in postmenopausal women.
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Authors | Ghada N Farhat, Steven R Cummings, Rowan T Chlebowski, Neeta Parimi, Jane A Cauley, Thomas E Rohan, Alison J Huang, Mara Vitolins, F Allan Hubbell, Joann E Manson, Barbara B Cochrane, Dorothy S Lane, Jennifer S Lee |
Journal | Journal of the National Cancer Institute
(J Natl Cancer Inst)
Vol. 103
Issue 7
Pg. 562-70
(Apr 06 2011)
ISSN: 1460-2105 [Electronic] United States |
PMID | 21330633
(Publication Type: Journal Article, Research Support, N.I.H., Extramural, Research Support, Non-U.S. Gov't)
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Chemical References |
- Biomarkers, Tumor
- Receptors, Estrogen
- Sex Hormone-Binding Globulin
- Testosterone
- Estradiol
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Topics |
- Aged
- Biomarkers, Tumor
(analysis)
- Breast Neoplasms
(blood, chemistry)
- Case-Control Studies
- Confounding Factors, Epidemiologic
- Estradiol
(blood)
- Female
- Humans
- Luminescent Measurements
- Middle Aged
- Postmenopause
- Proportional Hazards Models
- Prospective Studies
- Radioimmunoassay
- Receptors, Estrogen
(analysis)
- Risk Assessment
- Risk Factors
- Sex Hormone-Binding Globulin
(metabolism)
- Testosterone
(blood)
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