%0 Journal Article
%T Circulating free insulin-like growth factor-I and prostate cancer: a case-control study nested in the European prospective investigation into cancer and nutrition.
%A Cheng TS
%A Noor U
%A Watts E
%A Pollak M
%A Wang Y
%A McKay J
%A Atkins J
%A Masala G
%A Sánchez MJ
%A Agudo A
%A Castilla J
%A Aune D
%A Colorado-Yohar SM
%A Manfredi L
%A Gunter MJ
%A Pala V
%A Josefsson A
%A Key TJ
%A Smith-Byrne K
%A Travis RC
%J BMC Cancer
%V 24
%N 1
%D 2024 Jun 3
%M 38831273
%F 4.638
%R 10.1186/s12885-023-11425-w
%X <B>BACKGROUND: </B>Circulating total insulin-like growth factor-I (IGF-I) is an established risk factor for prostate cancer. However, only a small proportion of circulating IGF-I is free or readily dissociable from IGF-binding proteins (its bioavailable form), and few studies have investigated the association of circulating free IGF-I with prostate cancer risk.<BR><B>METHODS: </B>We analyzed data from 767 prostate cancer cases and 767 matched controls nested within the European Prospective Investigation into Cancer and Nutrition cohort, with an average of 14-years (interquartile range = 2.9) follow-up. Matching variables were study center, length of follow-up, age, and time of day and fasting duration at blood collection. Circulating free IGF-I concentration was measured in serum samples collected at recruitment visit (mean age 55 years old; standard deviation = 7.1) using an enzyme-linked immunosorbent assay (ELISA). Conditional logistic regressions were performed to examine the associations of free IGF-I with risk of prostate cancer overall and subdivided by time to diagnosis (≤ 14 and > 14 years), and tumor characteristics.<BR><B>RESULTS: </B>Circulating free IGF-I concentrations (in fourths and as a continuous variable) were not associated with prostate cancer risk overall (odds ratio [OR] = 1.00 per 0.1 nmol/L increment, 95% CI: 0.99, 1.02) or by time to diagnosis, or with prostate cancer subtypes, including tumor stage and histological grade.<BR><B>CONCLUSIONS: </B>Estimated circulating free IGF-I was not associated with prostate cancer risk. Further research may consider other assay methods that estimate bioavailable IGF-I to provide more insight into the well-substantiated association between circulating total IGF-I and subsequent prostate cancer risk.