Circulating levels of insulin‐like growth factor‐I and risk of ovarian cancer

Insulin‐like growth factor (IGF)‐I, a mitogenic and anti‐apoptotic peptide, has been implicated in the development of several cancers. We hypothesized that high circulating IGF‐I concentrations may be associated with an increased risk of ovarian cancer. A case–control study was nested within 3 prospective cohorts in New York (USA), Umeå (Sweden) and Milan (Italy). One hundred thirty‐two women with primary invasive epithelial ovarian cancer diagnosed at least 1 year after blood donation were case subjects. For each case, 2 control subjects were selected, matching the case subject on cohort, menopausal status, age and date of recruitment (n = 263). Only women who did not use exogenous hormones at blood donation were included in the study. There was no association between IGF‐I concentrations and ovarian cancer risk in the study group as a whole. In analyses restricted to subjects who had developed ovarian cancer at a young age (<55), circulating IGF‐I was directly and strongly associated with ovarian cancer risk (OR = 4.97; 95% CI = 1.22–20.2 for the top vs. the bottom IGF‐I tertile after adjustment for parity, BMI categories and smoking). There was no significant association of IGF binding protein‐3 with ovarian cancer risk. We found a strong direct relationship between circulating IGF‐I levels and risk of developing ovarian cancer before age 55. Additional, larger studies of this association are needed to provide more precise estimates of effect. © 2002 Wiley‐Liss, Inc.