Data from A Meta-analysis of Individual Participant Data Reveals an Association between Circulating Levels of IGF-I and Prostate Cancer Risk

<div>Abstract<p>The role of insulin-like growth factors (IGF) in prostate cancer development is not fully understood. To investigate the association between circulating concentrations of IGFs (IGF-I, IGF-II, IGFBP-1, IGFBP-2, and IGFBP-3) and prostate cancer risk, we pooled individual participant data from 17 prospective and two cross-sectional studies, including up to 10,554 prostate cancer cases and 13,618 control participants. Conditional logistic regression was used to estimate the ORs for prostate cancer based on the study-specific fifth of each analyte. Overall, IGF-I, IGF-II, IGFBP-2, and IGFBP-3 concentrations were positively associated with prostate cancer risk (<i>P</i><sub>trend</sub> all ≤ 0.005), and IGFBP-1 was inversely associated weakly with risk (<i>P</i><sub>trend</sub> = 0.05). However, heterogeneity between the prospective and cross-sectional studies was evident (<i>P</i><sub>heterogeneity</sub> = 0.03), unless the analyses were restricted to prospective studies (with the exception of IGF-II, <i>P</i><sub>heterogeneity</sub> = 0.02). For prospective studies, the OR for men in the highest versus the lowest fifth of each analyte was 1.29 (95% confidence interval, 1.16–1.43) for IGF-I, 0.81 (0.68–0.96) for IGFBP-1, and 1.25 (1.12–1.40) for IGFBP-3. These associations did not differ significantly by time-to-diagnosis or tumor stage or grade. After mutual adjustment for each of the other analytes, only IGF-I remained associated with risk. Our collaborative study represents the largest pooled analysis of the relationship between prostate cancer risk and circulating concentrations of IGF-I, providing strong evidence that IGF-I is highly likely to be involved in prostate cancer development. <i>Cancer Res; 76(8); 2288–300. ©2016 AACR</i>.</p></div>