IGF‐I and breast cancer: A meta‐analysis

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Abstract
IGFs are peptide hormones involved in the regulation of cell proliferation, differentiation and apoptosis. IGFs are regulated by endocrine and paracrine mechanisms; however, their action in tissue is determined by circulating levels and local production of IGFs and IGF‐binding proteins (IGFBPs). Some, but not all, epidemiologic studies have associated high circulating levels of IGF‐I with increased risk of breast cancer among premenopausal women. To evaluate the overall association of IGF‐I and IGFBP‐3 levels with breast cancer risk, we performed a meta‐analysis on 16 publications of epidemiologic and clinical studies. Analyses were performed for all women as well as for pre‐ and postmenopausal women separately. Hedges' standardized mean differences (HSMDs) and odds ratios (ORs) were used to estimate the effect of IGF‐I and IGFBP‐3. Data analysis showed that circulating levels of IGF‐I were not significantly higher in breast cancer patients than in controls for all women and for the postmenopausal group (HSMD = 0.024 and 0.035, respectively; p > 0.40) but were significantly higher (HSMD = 0.170, p < 0.001) for the premenopausal group. ORs for breast cancer risk were 1.05 (95% CI 0.94–1.17), 0.93 (95% CI 0.80–1.10) and 1.39 (95% CI 1.16–1.66). The HSMD of IGFBP‐3 was 0.18 (p < 0.001), and the OR for breast cancer was 1.42 (95% CI 1.15–1.74) for premenopausal women. Our results support the suggested association between high IGF‐I and IGFBP‐3 levels and increased risk of breast cancer in premenopausal women.

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