Circulating Insulin and C-Peptide Levels and Risk of Breast Cancer among Predominately Premenopausal Women
- A. Heather Eliassen1,2,
- Shelley S. Tworoger1,2,
- Christos S. Mantzoros3,
- Michael N. Pollak4 and
- Susan E. Hankinson1,2
- 1Channing Laboratory, Department of Medicine, Brigham and Women's Hospital and Harvard Medical School; 2Department of Epidemiology, Harvard School of Public Health; and 3Division of Endrocrinology, Diabetes, and Metabolism, Department of Medicine, Beth Israel Deaconess Medical Center, Boston, Massachusetts; and 4Departments of Medicine and Oncology, McGill University, Montreal, Quebec, Canada
- Requests for reprints:
Heather Eliassen, Channing Laboratory, Brigham and Women's Hospital, 181 Longwood Avenue, Boston, MA 02115. Phone: 617-525-2104; Fax: 617-525-2008. E-mail: heather.eliassen{at}channing.harvard.edu
Abstract
Insulin and insulin resistance have been hypothesized to increase the risk of breast cancer as insulin increases breast cell proliferation and inhibits sex hormone binding globulin. Although insulin is directly related to body weight, adiposity is inversely associated with breast cancer risk in premenopausal women but directly related to risk in postmenopausal women. To explore the association between insulin and c-peptide levels and breast cancer risk, we conducted a nested case-control study of predominantly premenopausal women within the Nurses' Health Study II cohort. From 1996 to 1999, blood samples were collected from 29,611 participants. A total of 317 cases were diagnosed after blood collection and before June 2003 and matched to 634 controls; 75% of these women were premenopausal at blood collection. Logistic regression models, controlling for breast cancer risk factors, were used to calculate relative risks (RR) and 95% confidence intervals (95% CI). Among women with fasting blood samples (n = 211 cases), insulin was suggestively inversely associated with breast cancer risk (highest versus lowest quartile: RR, 0.5; 95% CI, 0.3-1.0; Ptrend = 0.06). Among all women, c-peptide was not associated with breast cancer risk (highest versus lowest quartile: RR, 1.1; 95% CI, 0.7-1.7; Ptrend = 0.79); results were similar among fasting samples. These associations did not differ by age, body mass index, or waist-to-hip ratio. Overall, higher levels of insulin and c-peptide were not associated with a higher risk of breast cancer among predominantly premenopausal women. (Cancer Epidemiol Biomarkers Prev 2007;16(1):161–4)
Footnotes
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Grant support: National Cancer Institute research grants CA67262 and CA50385 and Cancer Education and Career Development grant R25 CA098566-02 (A.H. Eliassen).
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The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
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- Accepted November 3, 2006.
- Received August 14, 2006.
- Revision received October 30, 2006.
