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Relationship of Obesity and Physical Activity with C-Peptide, Leptin, and Insulin-Like Growth Factors in Breast Cancer Survivors

¹ Department of Epidemiology and Public Health, Yale School of Medicine, New Haven, Connecticut; ² The Fred Hutchinson Cancer Research Center, Seattle, Washington; ³ Department of Preventive Medicine, University of Southern California, Los Angeles, California; ⁴ University of New Mexico, Albuquerque, New Mexico; and ⁵ Applied Research Program, Division of Cancer Control and Population Sciences, National Cancer Institute, Bethesda, Maryland

Requests for reprints: Melinda L. Irwin, Department of Epidemiology and Public Health, Yale School of Medicine, P.O. Box 208034, New Haven, CT 06520-8034. Phone: 203-785-6392; Fax: 203-785-6279. E-mail: melinda.irwin{at}yale.edu

Introduction: Obese and physically inactive breast cancer patients may have poorer survival compared with lighter weight and more active women. Several obesity-related and physical activity–related hormones and peptides may explain this association, including insulin, leptin, insulin-like growth factor-I (IGF-I), and IGF-binding protein-3. Few studies have examined the associations between obesity, physical activity, and these hormones/peptides among breast cancer survivors.

Purpose: To determine whether obesity and physical activity are associated with insulin, IGFs, and leptin levels in a population-based sample of 710 women diagnosed with in situ to stage IIIA breast cancer and enrolled in the Health, Eating, Activity, and Lifestyle Study.

Methods: We collected a blood sample and information on physical activity among women diagnosed 2 to 3 years earlier using an interview-administered questionnaire. Trained staff measured weight. C-peptide, leptin, and IGFs were assayed by RIA. Mean hormone levels within body mass index and physical activity categories were adjusted for confounders using analysis of covariance methods.

Results: We observed higher C-peptide (P for trend = 0.0001) and leptin (P for trend = 0.0001) levels and lower IGF-I levels (P for trend = 0.0001) with higher levels of body mass index. We observed lower C-peptide (P for trend = 0.001) and leptin (P for trend = 0.001) levels and higher IGF-I (P for trend = 0.0037) and IGF-binding protein-3 (P for trend = 0.055) levels with higher levels of physical activity.

Conclusions: Increasing physical activity and decreasing body fat may be a reasonable intervention approach toward changing insulin and leptin, thereby potentially influencing breast cancer prognosis. (Cancer Epidemiol Biomarkers Prev 2005;14(12):2881–8)

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