title: Breast Cancer Subtype Variation by Race and Ethnicity in a Diverse Population in British Columbia.
abstract: BACKGROUND
  Breast cancer subtypes occur differentially across different racial and ethnic groups. However, their distribution within a multicultural population is unknown.
  
  
  METHODS
  Patients with invasive breast cancer newly diagnosed in 2006 and referred to the British Columbia Cancer Agency were identified from the Breast Cancer Outcomes Unit database. Race/ethnicity data were abstracted from a patient-completed health assessment questionnaire completed at the initial consultation, and grouped as white, East Asian, Aboriginal, South Asian, Southeast Asian, and other. Breast cancer subtypes were created using available data on estrogen receptor (ER), progesterone receptor (PR), and human epidermal growth factor receptor 2 (HER2) status.
  
  
  RESULTS
  A total of 1829 women had complete data. Of these women, 73% were white, 8% were East Asian, 4% Aboriginal, 3% South Asian, 3% Southeast Asian, and 3% other. The median age at diagnosis was 60 years; the youngest were Southeast Asian (51 years) and the oldest were white (60 years; P < .001). The overall ER positivity rate was 81%, highest in East Asian women (89%) and lowest in South Asian women (73%). The HER2 positivity rate was 16% for all patients and was highest in the South Asian (28%), Southeast Asian (28%), and Aboriginal (24%) women and lowest in the white women (14%; P < .001). Triple-negative (ER-, PR-, and HER2-negative) breast cancer was uncommon in East Asian women (5%) but more common in South Asian women (19%; P < .001). The 5-year breast cancer-specific survival was 90% (95% confidence interval, 89%-92%), with no significant difference among the racial/ethnic groups (P = .136).
  
  
  CONCLUSIONS
  Breast cancer subtypes varied by race/ethnicity in our cross-sectional cohort of a multicultural population, suggesting that race/ethnicity plays a significant role in the biology of invasive breast cancer.
authors.affiliation: Division of Medical Oncology, British Columbia Cancer Agency, Vancouver, BC, Canada.
authors.forename: Dante
authors.initials: D
authors.lastname: Wan
authors.affiliation: Division of Medical Oncology, British Columbia Cancer Agency, Vancouver, BC, Canada. Electronic address: dvilla@bccancer.bc.ca.
authors.forename: Diego
authors.initials: D
authors.lastname: Villa
authors.affiliation: Cancer Control Research, British Columbia Cancer Agency, Vancouver, BC, Canada.
authors.forename: Ryan
authors.initials: R
authors.lastname: Woods
authors.affiliation: Division of Medical Oncology, British Columbia Cancer Agency, Vancouver, BC, Canada; Division of Medical Oncology, Davidoff Center, Petah Tikvah, Israel.
authors.forename: Rinat
authors.initials: R
authors.lastname: Yerushalmi
authors.affiliation: Division of Medical Oncology, British Columbia Cancer Agency, Vancouver, BC, Canada.
authors.forename: Karen
authors.initials: K
authors.lastname: Gelmon
mesh_terms: D000368:Aged; D014408:Biomarkers, Tumor / Q000032:analysis; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000473:pathology*; D001955:British Columbia / Q000453:epidemiology; D015331:Cohort Studies; D003430:Cross-Sectional Studies; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D053208:Kaplan-Meier Estimate; D008875:Middle Aged; D010641:Phenotype; D016016:Proportional Hazards Models
chemical_list: D014408:Biomarkers, Tumor
keywords: Aboriginal; Asian; Breast cancer subtypes; Estrogen receptor; HER2