Association of circulating insulin-like growth factor 1 and insulin-like growth factor binding protein 3 with the risk of ovarian cancer: A systematic review and meta-analysis.

Insulin-like growth factor 1 (IGF-1) and its main binding protein (IGFBP-3) in blood have been associated with the risk of several types of cancer. However, epidemiological studies have inconsistent results regarding the association of circulating IGF-1/IGFBP-3 levels with ovarian cancer risk. A systematic review of the prospective studies was conducted using meta-analysis to evaluate the existing evidence. Pubmed and Embase databases were searched to identify the relevant studies published before May 1, 2014. Four highly qualified studies with a total of 627 cases and 1,358 controls were finally included in the meta-analysis. Random effects meta-analysis was conducted by combining study-specific odds ratios (ORs) of ovarian cancer for the highest verses lowest exposure levels. A dose-response association was further assessed by relating the log of ORs for different exposure levels. As a result, the pooled ORs for the highest verses lowest categories of IGF-1/IGFBP-3 were 0.85 [95% confidence interval (CI), 0.51-1.40]/0.78 (95% CI, 0.43-1.40). In the subgroup analyses, the pooled ORs of IGF-1/IGFBP-3 were 1.89 (95% CI, 0.64-5.59)/1.08 (95% CI, 0.50-2.32) for the subgroup with cases diagnosed at <55 years, and 0.74 (95% CI, 0.50-1.08)/0.98 (95% CI, 0.73-1.33) for the subgroup with cases diagnosed at ≥55 years. No linear association between circulating IGF-1/IGFBP-3 levels and ovarian cancer risk was identified. As no significant association of IGF-1/IGFBP-3 with ovarian cancer risk was identified in the present meta-analysis of existing studies, more studies with greater quality are required in the future.