title: Randomized controlled trial of aerobic exercise on insulin and insulin-like growth factors in breast cancer survivors: the Yale Exercise and Survivorship study.
abstract: BACKGROUND
  High insulin and insulin-like growth factor-I (IGF-I) levels may be associated with an increased breast cancer risk and/or death. Given the need to identify modifiable factors that decrease insulin, IGF-I, and breast cancer risk and death, we investigated the effects of a 6-month randomized controlled aerobic exercise intervention versus usual care on fasting insulin, IGF-I, and its binding protein (IGFBP-3) in postmenopausal breast cancer survivors.
  
  
  METHODS
  Seventy-five postmenopausal breast cancer survivors were identified from the Yale-New Haven Hospital Tumor Registry and randomly assigned to an exercise (n = 37) or usual care (n = 38) group. The exercise group participated in 150 minutes per week of moderate-intensity aerobic exercise. The usual care group was instructed to maintain their current physical activity level. A fasting blood sample was collected on each study participant at baseline and 6 months. Blood levels of insulin and IGF were measured with ELISA.
  
  
  RESULTS
  On average, exercisers increased aerobic exercise by 129 minutes per week compared with 45 minutes per week among usual care participants (P < 0.001). Women randomized to exercise experienced decreases in insulin, IGF-I, and IGFBP-3, whereas women randomized to usual care had increases in these hormones. Between-group differences in insulin, IGF-I, and IGFBP-3 were 20.7% (P = 0.089), 8.9% (P = 0.026), and 7.9% (P = 0.006), respectively.
  
  
  CONCLUSIONS
  Moderate-intensity aerobic exercise, such as brisk walking, decreases IGF-I and IGFBP-3. The exercise-induced decreases in IGF may mediate the observed association between higher levels of physical activity and improved survival in women diagnosed with breast cancer.
authors.affiliation: Department of Epidemiology and Public Health, Yale School of Medicine, P.O. Box 208034, New Haven, CT 06520-8034, USA. melinda.irwin@yale.edu
authors.forename: Melinda L
authors.initials: ML
authors.lastname: Irwin
authors.forename: Katie
authors.initials: K
authors.lastname: Varma
authors.forename: Marty
authors.initials: M
authors.lastname: Alvarez-Reeves
authors.forename: Lisa
authors.initials: L
authors.lastname: Cadmus
authors.forename: Andrew
authors.initials: A
authors.lastname: Wiley
authors.forename: Gina G
authors.initials: GG
authors.lastname: Chung
authors.forename: Loretta
authors.initials: L
authors.lastname: Dipietro
authors.forename: Susan T
authors.initials: ST
authors.lastname: Mayne
authors.forename: Herbert
authors.initials: H
authors.lastname: Yu
mesh_terms: D015502:Absorptiometry, Photon; D000886:Anthropometry; D015519:Bone Density; D001943:Breast Neoplasms / Q000097:blood*; D016009:Chi-Square Distribution; D004797:Enzyme-Linked Immunosorbent Assay; D015444:Exercise; D005260:Female; D006801:Humans; D007328:Insulin / Q000378:metabolism*; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000097:blood; D016014:Linear Models; D008875:Middle Aged; D012306:Risk; D013002:Somatomedins / Q000378:metabolism*; D011795:Surveys and Questionnaires; D017741:Survivors
chemical_list: D007328:Insulin; D018972:Insulin-Like Growth Factor Binding Protein 3; D013002:Somatomedins