title: BMI, reproductive factors, and breast cancer molecular subtypes: A case-control study and meta-analysis.
abstract: BACKGROUND
  The effects of body mass index (BMI) and reproductive factors may vary among breast cancer molecular subtypes, evidence of which is lacking in East Asia.
  
  
  METHODS
  From 2002 to 2010, 1256 breast cancer patients and 1416 healthy women were recruited. Anthropometric and reproductive factors were collected from medical charts. Breast cancer subtype was defined by ER, PR, and HER2 status. Polytomous logistic regression was used to evaluate associations between risk factors and breast cancer subtypes, with subgroup analysis by menopausal status. A meta-analysis of relevant published studies in East Asia was also performed.
  
  
  RESULTS
  In our case-control study, late menarche was negatively associated with luminal tumor risk (Ptrend= 0.03). Higher BMI was associated with risk of both luminal and triple-negative tumors (Ptrend<0.001). Late age at first live birth was associated with a 1.41- to 2.08-fold increased risk of all subtypes, while late menopause increased risk by 2.62-5.56 times. Heterogeneity of these associations was not detected for different menopausal statuses. The meta-analysis revealed a positive dose-response relationship between BMI and risk of both luminal and ER-PR- subtypes (Ptrend<0.05). Early menarche and nulliparity increased luminal tumor risk by 1.39 and 1.26 times, respectively. Non-breastfeeding also increased the risk of all subtypes.
  
  
  CONCLUSIONS
  For East Asian women, overweight, late menopause, and lack of breastfeeding appear to increase risk of both luminal and ER-PR- tumors. Early menarche and nulliparity mainly impacted luminal tumor risk. These associations were not impacted by menopausal status.
authors.affiliation: Department of Epidemiology and Biostatistics, West China School of Public Health, Sichuan University, Chengdu, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Xuezheng
authors.initials: X
authors.lastname: Sun
authors.affiliation: Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: Erline
authors.initials: E
authors.lastname: Miller
authors.affiliation: Department of Epidemiology and Biostatistics, West China School of Public Health, Sichuan University, Chengdu, China; Department of Health Service Management, Public Health School, Sun Yat-Sen University, Guangzhou, Guangdong, China.
authors.forename: Qiong
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Department of Breast Surgery, Sichuan Cancer Hospital, Chengdu, China.
authors.forename: Ping
authors.initials: P
authors.lastname: Tao
authors.affiliation: The Comprehensive Guidance Center of Women's Health, Chengdu Women's and Children's Central Hospital, Chengdu, China.
authors.forename: Li
authors.initials: L
authors.lastname: Liu
authors.affiliation: Department of Epidemiology and Biostatistics, West China School of Public Health, Sichuan University, Chengdu, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: Department of Epidemiology and Biostatistics, West China School of Public Health, Sichuan University, Chengdu, China.
authors.forename: Mengjie
authors.initials: M
authors.lastname: Wang
authors.affiliation: Department of Epidemiology and Biostatistics, West China School of Public Health, Sichuan University, Chengdu, China.
authors.forename: Yana
authors.initials: Y
authors.lastname: Qi
authors.affiliation: Department of Epidemiology and Biostatistics, West China School of Public Health, Sichuan University, Chengdu, China. Electronic address: lijiayuan73@163.com.
authors.forename: Jiayuan
authors.initials: J
authors.lastname: Li
mesh_terms: D000328:Adult; D000367:Age Factors; D015992:Body Mass Index; D001942:Breast Feeding / Q000706:statistics & numerical data; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000473:pathology*; D016022:Case-Control Studies; D005202:Asia, Eastern / Q000453:epidemiology; D005260:Female; D006801:Humans; D008572:Menarche; D008593:Menopause; D008875:Middle Aged; D050177:Overweight / Q000453:epidemiology; D010298:Parity; D011247:Pregnancy; D055703:Reproductive Physiological Phenomena; D012307:Risk Factors
keywords: Body mass index; Breast cancer; East Asia; Molecular subtype; Reproductive factor