title: Reproductive factors and subtypes of breast cancer defined by estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2: a register-based study from Korea.
abstract: BACKGROUND
  The relationship between reproductive breast risk factors and breast cancer survival in patients with different breast cancer subtypes is not well known.
  
  
  METHODS
  We examined a large-sized, retrospective study of 23,882 subjects from the Korean Breast Cancer Registry. The breast cancer subtype was determined by immunohistochemical staining for estrogen receptor, progesterone receptor, and human epidermal growth factor receptor 2 (HER2). Information regarding reproductive factors, including breastfeeding, age at first birth (AFB), and parity, was gathered. Multivariate Cox regression analysis was used to estimate the association among breast cancer subtypes, such as luminal A, luminal B, Her-2/neu overexpressing, and triple negative breast cancer (TNBC), and breast cancer survival as dependent variables and adjusting for age and stage.
  
  
  RESULTS
  High parity (≥ 5) increased the recurrence risk of luminal A and B breast cancer (hazard ratio [HR], 1.95; 95% confidence interval [CI], 0.96-3.97; P = .0055 and HR, 1.12; 95% CI, 0.42-3.02, respectively; P = .0073) in breast cancer-specific survival (BCSS), but 1 to 3 child births decreased the recurrence risk of luminal A breast cancer (HR, 0.56; 95% CI, 0.34-0.91; P = .0055) and luminal B breast cancer (HR, 0.32; 95% CI, 0.17-0.61; P = .0073) in BCSS. Early AFB (< 20 years) increased the recurrence risk of luminal A breast cancers (HR, 1.61; 95% CI, 0.62-4.26; P = .039) in BCSS and of TNBC (HR, 1.31; 95% CI, 0.78-2.21; P = .0006) in overall survival. Her-2/neu overexpressing breast cancer had no correlation with parity and AFB in breast cancer survival.
  
  
  CONCLUSIONS
  High parity (≥ 5) and early AFB (< 20 years) were correlated with worse clinical outcomes in patients with luminal breast cancer, but not with other subtyped breast cancers.
authors.affiliation: Department of Surgery, Haeundae Paik Hospital, College of Medicine, University of Inje, Gimhae, Korea. Electronic address: gsjslee@gmail.com.
authors.forename: Jung Sun
authors.initials: JS
authors.lastname: Lee
authors.affiliation: Department of Pharmacology, College of Medicine, University of Inje, Clinical Trial Center, Gimhae, Korea.
authors.forename: Minkyung
authors.initials: M
authors.lastname: Oh
mesh_terms: D000328:Adult; D001741:Black or African American / Q000706:statistics & numerical data*; D000367:Age Factors; D014408:Biomarkers, Tumor / Q000378:metabolism; D001943:Breast Neoplasms / Q000453:epidemiology / Q000378:metabolism* / Q000473:pathology*; D016022:Case-Control Studies; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008593:Menopause; D008875:Middle Aged; D060787:Neoplasm Grading; D009367:Neoplasm Staging; D011379:Prognosis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*; D011960:Receptors, Estrogen / Q000378:metabolism*; D011980:Receptors, Progesterone / Q000378:metabolism*; D012042:Registries; D017584:Reproductive History; D056910:Republic of Korea / Q000453:epidemiology; D012189:Retrospective Studies; D012307:Risk Factors; D015996:Survival Rate; D044465:White People / Q000706:statistics & numerical data*
chemical_list: D014408:Biomarkers, Tumor; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; C508053:ERBB2 protein, human
keywords: Breast Cancer Subtype; Breast Cancer Survival; Breastfeeding; Reproduction