title: Longitudinal changes in IGF-I and IGFBP-3, and mammographic density among postmenopausal women.
abstract: A relation between the breast cancer risk factors, insulin-like growth factor-I (IGF-I) and mammographic density, is biologically plausible, but results from cross-sectional epidemiologic studies have been mixed. Our objective was to examine the relation in a longitudinal manner, that is, between the change in circulating IGF-I concentrations and the change in mammographic measures over one year. Data from an exercise intervention trial conducted in 302 postmenopausal women ages 50 to 74 years were used. Blood drawn at baseline and postintervention was assessed for IGF-I and its binding protein (IGFBP-3) by direct chemiluminscent immunoassay. Area and volumetric measurements of mammographic dense fibroglandular and nondense fatty tissue were made. Statistical analyses were based on multiple linear regression. A one SD (20.2 ng/mL) change in IGF-I over one year was associated with small changes in percent dense area [mean: 0.8%; 95% confidence interval (CI), 0.1-1.4] and dense area (mean: 1.2 cm(2); 95% CI, 0.2-2.1). Change in IGFBP-3 was also associated with percent and absolute dense area. Absolute and percent dense volume, and mammographic measures representing fatty tissue (nondense area and volume) were not associated with changes in IGF-I and IGFBP-3. Longitudinal associations may be more detectable than cross-sectional associations due to the absence of confounding by invariant personal factors. Absolute and percent dense area, measures that are related to breast cancer risk, may be affected by IGF-I. Confirmation should be sought in further longitudinal studies in which larger changes in the IGF system are evoked.
authors.affiliation: Authors' Affiliations: Obstetrics & Gynaecology and Pediatrics, Dalhousie University, Halifax, Nova Scotia; Faculty of Physical Education and Recreation, University of Alberta; Cross Cancer Institute, Alberta Cancer Board, Edmonton; Alberta Health Services, Calgary, Alberta; Campbell Family Institute for Breast Cancer Research, Ontario Cancer Institute; Sunnybrook Research Institute, Toronto, Ontario; Department of Statistics, University of British Columbia, Vancouver; Southern Medical Program, University of British Columbia (Okanagan Campus), Kelowna, British Columbia, Canada; Fred Hutchison Cancer Research Center, Seattle, Washington; Keck School of Medicine, University of Southern California, Los Angeles, California; and Department of Internal Medicine, University of New Mexico, Albuquerque, New Mexico.
authors.forename: Christy G
authors.initials: CG
authors.lastname: Woolcott
authors.forename: Kerry S
authors.initials: KS
authors.lastname: Courneya
authors.forename: Norman F
authors.initials: NF
authors.lastname: Boyd
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Yaffe
authors.forename: Anne
authors.initials: A
authors.lastname: McTiernan
authors.forename: Rollin
authors.initials: R
authors.lastname: Brant
authors.forename: Charlotte A
authors.initials: CA
authors.lastname: Jones
authors.forename: Frank Z
authors.initials: FZ
authors.lastname: Stanczyk
authors.forename: Tim
authors.initials: T
authors.lastname: Terry
authors.forename: Linda S
authors.initials: LS
authors.lastname: Cook
authors.forename: Qinggang
authors.initials: Q
authors.lastname: Wang
authors.forename: Christine M
authors.initials: CM
authors.lastname: Friedenreich
mesh_terms: D000368:Aged; D001940:Breast / Q000473:pathology*; D005260:Female; D006801:Humans; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000032:analysis / Q000097:blood / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000032:analysis / Q000378:metabolism*; D008137:Longitudinal Studies; D008327:Mammography; D008875:Middle Aged; D017698:Postmenopause / Q000097:blood*; D016032:Randomized Controlled Trials as Topic; D012307:Risk Factors
chemical_list: D018972:Insulin-Like Growth Factor Binding Protein 3; D007334:Insulin-Like Growth Factor I