title: Effects of childhood body size on breast cancer tumour characteristics.
abstract: BACKGROUND
  Although a role of childhood body size in postmenopausal breast cancer risk has been established, less is known about its influence on tumour characteristics.
  
  
  METHODS
  We studied the relationships between childhood body size and tumour characteristics in a Swedish population-based case-control study consisting of 2,818 breast cancer cases and 3,111 controls. Our classification of childhood body size was derived from a nine-level somatotype. Relative risks were estimated by odds ratios with 95% confidence intervals, derived from fitting unconditional logistic regression models. Association between somatotype at age 7 and tumour characteristics were evaluated in a case-only analysis where P values for heterogeneity were obtained by performing one degree of freedom trend tests.
  
  
  RESULTS
  A large somatotype at age 7 was found to be associated with decreased postmenopausal breast cancer risk. Although strongly associated with other risk factors such as age of menarche, adult body mass index and mammographic density, somatotype at age 7 remained a significant protective factor (odds ratio (OR) comparing large to lean somatotype at age 7 = 0.73, 95% confidence interval (CI) = 0.58-0.91, P trend = 0.004) after adjustment. The significant protective effect was observed within all subgroups defined by estrogen receptor (ER) and progesterone receptor (PR) status, with a stronger effect for ER-negative (0.40, 95% CI = 0.21-0.75, P trend = 0.002), than for ER-positive (0.80, 95% CI = 0.62-1.05, P trend = 0.062), tumours (P heterogeneity = 0.046). Somatotype at age 7 was not associated with tumour size, histology, grade or the presence or absence of metastatic nodes.
  
  
  CONCLUSIONS
  Greater body size at age 7 is associated with a decreased risk of postmenopausal breast cancer, and the associated protective effect is stronger for the ER-negative breast cancer subtype than for the ER-positive subtype.
authors.affiliation: Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden. jingmei.li@ki.se
authors.forename: Jingmei
authors.initials: J
authors.lastname: Li
authors.forename: Keith
authors.initials: K
authors.lastname: Humphreys
authors.forename: Louise
authors.initials: L
authors.lastname: Eriksson
authors.forename: Kamila
authors.initials: K
authors.lastname: Czene
authors.forename: Jianjun
authors.initials: J
authors.lastname: Liu
authors.forename: Per
authors.initials: P
authors.lastname: Hall
mesh_terms: D000368:Aged; D015992:Body Mass Index; D049628:Body Size / Q000502:physiology*; D001943:Breast Neoplasms / Q000378:metabolism / Q000473:pathology* / Q000503:physiopathology*; D016022:Case-Control Studies; D002648:Child; D005260:Female; D006801:Humans; D016015:Logistic Models; D008207:Lymphatic Metastasis; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D011960:Receptors, Estrogen / Q000032:analysis; D011980:Receptors, Progesterone / Q000032:analysis; D018570:Risk Assessment / Q000379:methods; D012307:Risk Factors; D047368:Tumor Burden
chemical_list: D011960:Receptors, Estrogen; D011980:Receptors, Progesterone
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