Prospective study of IGF-I,IGF-binding proteins,and breast cancer risk,in northern and southern Sweden |
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Authors: | Kaaks Rudolf Lundin Eva Rinaldi Sabina Manjer Jonas Biessy Carine Söderberg Stefan Lenner Per Janzon Lars Riboli Elio Berglund Göran Hallmans Göran |
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Affiliation: | (1) Unit of Nutrition and Cancer, International Agency for Research on Cancer, 150 Cours Albert Thomas, 69372 Lyon Cedex 08, France;(2) University of Umeå, Sweden;(3) Lund University, UMAS, 205 02 Malmö, Sweden |
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Abstract: | Objective: To examine the possible relationships of breast cancer risk to prediagnostic plasma levels of insulin; insulin-like growth factor-I (IGF-I); and IGF-binding proteins -1, -2, and -3. Methods: Within two prospective cohorts in Umeå and Malmö we measured plasma concentrations of insulin, IGF-I, and IGFBPs for a total of 513 incident breast cancer cases and 987 matched controls. Results: Globally, risk was unassociated with levels of IGF-I, IGFBP-3, or IGF-I adjusted for IGFBP-3. When breaking down the analysis by subgroups of age at blood donation, an increase in risk was observed for increasing levels of IGF-I in women aged 55 or older, in the Umeå cohort only (odds ratios of 1.00, 1.73, 1.76, 1.90; ptrend = 0.05). This effect weakened, however, when the analysis was restricted to subjects who did not use exogenous hormones for the treatment of menopausal symptoms. Levels of IGF-I and IGFBP-3 were not related to risk in younger women, recruited before age 50, contrary to observations from previous studies. In a subcohort where blood samples had been collected after at least four hours of fasting, breast cancer risk showed no clear associations with levels of insulin, IGFBP-1, or IGFBP-2. Conclusions: Our results do not confirm earlier findings of an association of plasma IGF-I levels with breast cancer risk especially in young women, but suggest a possible association with postmenopausal breast cancer risk, possibly among ERT/HRT users only. Our results do not support the hypothesis that elevated plasma insulin levels, and reduced levels of IGFBP-1 and IGFBP-2, are associated with increased breast cancer risk. |
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Keywords: | breast cancer insulin IGF-I IGFBP-1 IGFBP-2 |
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