Circulating free insulin-like growth factor-I and prostate cancer: a case-control study nested in the European prospective investigation into cancer and nutrition.

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.

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.

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.

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.

BMC cancer. 2024 Jun 03*** epublish ***

Tuck Seng Cheng, Urwah Noor, Eleanor Watts, Michael Pollak, Ye Wang, James McKay, Joshua Atkins, Giovanna Masala, Maria-Jose Sánchez, Antonio Agudo, Jesús Castilla, Dagfinn Aune, Sandra M Colorado-Yohar, Luca Manfredi, Marc J Gunter, Valeria Pala, Andreas Josefsson, Timothy J Key, Karl Smith-Byrne, Ruth C Travis

Cancer Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, Richard Doll Building, Old Road Campus, Oxford, OX3 7LF, UK., Division of Cancer Epidemiology and Genetics, National Cancer Institute, Rockville, MD, USA., Oncology Department, McGill University and Segal Cancer Centre, Jewish General Hospital, Montreal, QC, Canada., Genomic Epidemiology Branch, International Agency for Research on Cancer, Lyon, France., Cancer Risk Factors and Life-Style Epidemiology Unit, Institute for Cancer Research, Prevention and Clinical Network (ISPRO), Florence, Italy., Escuela Andaluza de Salud Pública (EASP), Granada, 18011, Spain., Unit of Nutrition and Cancer, Catalan Institute of Oncology - ICO, L'Hospitalet de Llobregat, Barcelona, Spain., Instituto de Salud Pública de Navarra - IdiSNA, Pamplona, Spain., Department of Epidemiology and Biostatistics, School of Public Health, Imperial College London, London, UK., Department of Epidemiology, Murcia Regional Health Council-IMIB, Murcia, Spain., Centre for Biostatistics, Epidemiology, and Public Health (C-BEPH), Department of Clinical and Biological Sciences, University of Turin, Orbassano, TO, Italy., Nutrition and Metabolism Branch, International Agency for Research on Cancer (IARC- WHO), Lyon, France., Epidemiology and Prevention Unit, Department of Research, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy., Department of Urology, Institute of Clinical Sciences, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden., Cancer Epidemiology Unit, Nuffield Department of Population Health, University of Oxford, Richard Doll Building, Old Road Campus, Oxford, OX3 7LF, UK. .