Insulin growth factor (IGF) 1, IGF-binding proteins and ovarian cancer risk: A systematic review and meta-analysis

Background: Insulin resistance (IR) has been implicated in carcinogenesis, but there is no consensus regarding its involvement in ovarian cancer. We performed a systematic review and meta-analysis to evaluate the association between IR and ovarian cancer. Methods: Searches were conducted in five databases for studies evaluating IR markers (levels of serum insulin, C peptide, insulin growth factor [IGF] I and IGF-binding proteins [IGFBPs], homeostatic model assessment insulin resistance, and quantitative insulin-sensitivity check index) and ovarian cancer risk. Study selection, data extraction and an assessment of risk of bias were performed independently by three researchers. The associations between IR markers and ovarian cancer were quantified as mean differences (MDs) or standardized MDs (SMDs) and their 95% CIs using random-effect's models. Results: Fourteen case-control studies satisfied our inclusion criteria (n = 8130). There was little information on IR markers with the exception of the IGF system. Ovarian cancer was associated with lower IGF-1 levels (SMD -0.43 ngimL, 95% CI -0.67 to -0.18; p = 0.0006), and lower IGFBP-3 levels (SMD -0.11 ng/mL, 95% CI -0.21 to -0.00; p = 0.04). However, ovarian cancer was associated with higher levels of IGFBP-2 and IGFBP-1 (MD 527.3 ng/mL, 95%Cl 473.6, 581.0; p < 0.00001, and MD 3.47 ng/mL, 95%CI 1.42, 5.52; p = 0.0009 respectively). Subgroup analyses by menopausal status and age (<= 55 vs >55y) for IGF-1 and IGFBP-3 showed the subgroups were similar, although heterogeneity remained high. Conclusion: The evidence suggests that levels of IGF-1 and IGFBP-3 are lower in patients with ovarian cancer. In contrast, higher levels of IGBP-2 and IGBP-1 are found in patients with ovarian cancer. (C) 2016 Elsevier Ireland Ltd. All rights reserved.