title: Breast cancer subtypes and the risk of local and regional relapse.
abstract: OBJECTIVE
  The risk of local and regional relapse associated with each breast cancer molecular subtype was determined in a large cohort of patients with breast cancer. Subtype assignment was accomplished using a validated six-marker immunohistochemical panel applied to tissue microarrays.
  
  
  METHODS
  Semiquantitative analysis of estrogen receptor (ER), progesterone receptor (PR), Ki-67, human epidermal growth factor receptor 2 (HER2), epidermal growth factor receptor (EGFR), and cytokeratin (CK) 5/6 was performed on tissue microarrays constructed from 2,985 patients with early invasive breast cancer. Patients were classified into the following categories: luminal A, luminal B, luminal-HER2, HER2 enriched, basal-like, or triple-negative phenotype-nonbasal. Multivariable Cox analysis was used to determine the risk of local or regional relapse associated the intrinsic subtypes, adjusting for standard clinicopathologic factors.
  
  
  RESULTS
  The intrinsic molecular subtype was successfully determined in 2,985 tumors. The median follow-up time was 12 years, and there have been a total of 325 local recurrences and 227 regional lymph node recurrences. Luminal A tumors (ER or PR positive, HER2 negative, Ki-67 < 1%) had the best prognosis and the lowest rate of local or regional relapse. For patients undergoing breast conservation, HER2-enriched and basal subtypes demonstrated an increased risk of regional recurrence, and this was statistically significant on multivariable analysis. After mastectomy, luminal B, luminal-HER2, HER2-enriched, and basal subtypes were all associated with an increased risk of local and regional relapse on multivariable analysis.
  
  
  CONCLUSIONS
  Luminal A tumors are associated with a low risk of local or regional recurrence. Molecular subtyping of breast tumors using a six-marker immunohistochemical panel can identify patients at increased risk of local and regional recurrence.
authors.affiliation: Department of Radiation Oncology, British Columbia Cancer Agency, Vancouver, British Columbia, Canada V5Z 4E6. dvoduc@bccancer.bc.ca
authors.forename: K David
authors.initials: KD
authors.lastname: Voduc
authors.forename: Maggie C U
authors.initials: MC
authors.lastname: Cheang
authors.forename: Scott
authors.initials: S
authors.lastname: Tyldesley
authors.forename: Karen
authors.initials: K
authors.lastname: Gelmon
authors.forename: Torsten O
authors.initials: TO
authors.lastname: Nielsen
authors.forename: Hagen
authors.initials: H
authors.lastname: Kennecke
mesh_terms: D000328:Adult; D014408:Biomarkers, Tumor / Q000032:analysis; D001943:Breast Neoplasms / Q000401:mortality* / Q000473:pathology*; D066246:ErbB Receptors / Q000378:metabolism; D005260:Female; D006801:Humans; D019394:Ki-67 Antigen / Q000378:metabolism; D008207:Lymphatic Metastasis; D008875:Middle Aged; D009362:Neoplasm Metastasis; D009364:Neoplasm Recurrence, Local; D009376:Neoplasms, Hormone-Dependent; D011960:Receptors, Estrogen / Q000032:analysis; D011980:Receptors, Progesterone / Q000032:analysis; D046888:Tissue Array Analysis
chemical_list: D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone; D066246:ErbB Receptors