title: Association of body mass index with risk of luminal A but not luminal B estrogen receptor-positive and HER2-negative breast cancer for postmenopausal Japanese women.
abstract: BACKGROUND
  The impact of body mass index (BMI) on the risk of postmenopausal estrogen receptor (ER)-positive breast cancers has been well documented. However, the mechanism for the impact of BMI on the etiology of luminal A and luminal B subtypes has not yet been identified.
  
  
  METHODS
  We analyzed associations between BMI and breast cancers stratified by immunohistochemically defined intrinsic subtypes, and 1,297 Japanese women (615 breast cancer patients and 682 healthy women from a breast cancer screening program) were enrolled in a case-control study. ER-positive/human epidermal growth factor receptor 2 (HER2)-negative breast cancers were classified into luminal A and B subtypes according to Ki67 expression levels.
  
  
  RESULTS
  Higher BMI was significantly positively associated with postmenopausal breast cancer risk for one-unit increase in BMI (adjusted odds ratio (aOR) 1.09, 95 % confidence interval (CI) 1.04-1.15; P = 0.0008). Analyses of postmenopausal women revealed that BMI was consistently and exclusively associated with luminal A incidence (aOR 1.18, 95 % CI 1.10-1.26; P < 0.0001). When BMI was divided into three categories corresponding to those of controls, among postmenopausal women, the observed positive association was confined to luminal A (high vs low, aOR 2.98, 95 % CI 1.53-5.80; P < 0.005), but not luminal B (aOR 0.95, 95 % CI 0.47-1.91) subtypes.
  
  
  CONCLUSIONS
  We observed that BMI was significantly positively associated with increased risk of postmenopausal breast cancer for Japanese women with luminal A, but not with luminal B tumor subtype.
authors.affiliation: Division of Breast and Endocrine, Department of Surgery, Hyogo College of Medicine, Mukogawa-cho 1-1, Nishinomiya, Hyogo, 663-8501, Japan.
authors.forename: Yoshimasa
authors.initials: Y
authors.lastname: Miyagawa
authors.forename: Tomohiro
authors.initials: T
authors.lastname: Miyake
authors.forename: Ayako
authors.initials: A
authors.lastname: Yanai
authors.forename: Keiko
authors.initials: K
authors.lastname: Murase
authors.forename: Michiko
authors.initials: M
authors.lastname: Imamura
authors.forename: Shigetoshi
authors.initials: S
authors.lastname: Ichii
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Takatsuka
authors.forename: Takashi
authors.initials: T
authors.lastname: Ito
authors.forename: Seiichi
authors.initials: S
authors.lastname: Hirota
authors.forename: Masaru
authors.initials: M
authors.lastname: Saito
authors.forename: Yoshinao
authors.initials: Y
authors.lastname: Kotoura
authors.forename: Keisuke
authors.initials: K
authors.lastname: Miyauchi
authors.forename: Yasuhisa
authors.initials: Y
authors.lastname: Fujimoto
authors.forename: Takuya
authors.initials: T
authors.lastname: Hatada
authors.forename: Mitsunori
authors.initials: M
authors.lastname: Sasa
authors.forename: Yasuo
authors.initials: Y
authors.lastname: Miyoshi
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D044466:Asian People; D014408:Biomarkers, Tumor / Q000378:metabolism; D015992:Body Mass Index; D001943:Breast Neoplasms / Q000453:epidemiology / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D008875:Middle Aged; D017698:Postmenopause; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism*; D012307:Risk Factors; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; C508053:ERBB2 protein, human