title: IGF-I during primiparous pregnancy and maternal risk of breast cancer.
abstract: Previously, we reported that insulin-like growth factor (IGF)-I during early pregnancy is positively associated with maternal risk of breast cancer. To further explore this association, we designed a new study limited to women who donated a blood sample during their first pregnancy ending with childbirth. A case-control study was nested within the Northern Sweden Maternity Cohort in which repository since 1975, serum specimens remaining after early pregnancy screening for infectious diseases had been preserved. Study subjects were selected among women who donated a blood sample during the full-term pregnancy that led to the birth of their first child. Two hundred and forty-four women with invasive breast cancer were eligible. Two controls, matching the index case for age and date at blood donation were selected (n = 453). IGF-I was measured in serum samples on an Immulite 2000 analyzer. Conditional logistic regression was used to estimate odds ratios and 95% confidence intervals. A significant positive association of breast cancer with IGF-I was observed, with OR of 1.73 (95% CI: 1.14-2.63) for the top tertile, P < 0.009. Subgroup analyses did not indicate statistical heterogeneity of the association by ages at sampling and diagnosis or by lag time to cancer diagnosis, although somewhat stronger associations with risk were observed in women < or = age 25 at index pregnancy and for cases diagnosed within 15 years of blood donation. The results of the study add further evidence for an adverse effect of elevated IGF-I concentrations during early reproductive life on risk of breast cancer.
authors.affiliation: Division of Cancer Epidemiology, German Cancer Research Center, Heidelberg, Germany.
authors.forename: Tianhui
authors.initials: T
authors.lastname: Chen
authors.forename: Annekatrin
authors.initials: A
authors.lastname: Lukanova
authors.forename: Kjell
authors.initials: K
authors.lastname: Grankvist
authors.forename: Anne
authors.initials: A
authors.lastname: Zeleniuch-Jacquotte
authors.forename: Marianne
authors.initials: M
authors.lastname: Wulff
authors.forename: Robert
authors.initials: R
authors.lastname: Johansson
authors.forename: Helena
authors.initials: H
authors.lastname: Schock
authors.forename: Per
authors.initials: P
authors.lastname: Lenner
authors.forename: Goran
authors.initials: G
authors.lastname: Hallmans
authors.forename: Goran
authors.initials: G
authors.lastname: Wadell
authors.forename: Paolo
authors.initials: P
authors.lastname: Toniolo
authors.forename: Eva
authors.initials: E
authors.lastname: Lundin
mesh_terms: D000328:Adult; D001943:Breast Neoplasms / Q000097:blood*; D016022:Case-Control Studies; D005260:Female; D020073:Gravidity; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000032:analysis* / Q000378:metabolism*; D016017:Odds Ratio; D011247:Pregnancy / Q000097:blood*; D012307:Risk Factors
chemical_list: D007334:Insulin-Like Growth Factor I