title: Can breast cancer molecular subtype help to select patients for preoperative MR imaging?
abstract: OBJECTIVE
  To assess whether breast cancer molecular subtype classified by surrogate markers can be used to predict the extent of clinically relevant disease with preoperative breast magnetic resonance (MR) imaging.
  
  
  METHODS
  In this HIPAA-compliant, institutional review board-approved study, informed consent was waived. Preoperative breast MR imaging reports from 441 patients were reviewed for multicentric and/or multifocal disease, lymph node involvement, skin and/or nipple invasion, chest wall and/or pectoralis muscle invasion, or contralateral disease. Pathologic reports were reviewed to confirm the MR imaging findings and for hormone receptors (estrogen and progesterone subtypes), human epidermal growth factor receptor type 2 (HER2 subtype), tumor size, and tumor grade. Surrogates were used to categorize tumors by molecular subtype: hormone receptor positive and HER2 negative (luminal A subtype); hormone receptor positive and HER2 positive (luminal B subtype); hormone receptor negative and HER2 positive (HER2 subtype); hormone receptor negative and HER2 negative (basal subtype). All patients included in the study had a histologic correlation with MR imaging findings or they were excluded. χ(2) analysis was used to compare differences between subtypes, with multivariate logistic regression analysis used to assess for variable independence.
  
  
  RESULTS
  Identified were 289 (65.5%) luminal A, 45 (10.2%) luminal B, 26 (5.9%) HER2, and 81 (18.4%) basal subtypes. Among subtypes, significant differences were found in the frequency of multicentric and/or multifocal disease (luminal A, 27.3% [79 of 289]; luminal B, 53.3% [24 of 45]; HER2, 65.4% [17 of 26]; basal, 27.2% [22 of 81]; P < .001) and lymph node involvement (luminal A, 17.3% [50 of 289]; luminal B, 35.6% [26 of 45]; HER2, 34.6% [nine of 26]; basal 24.7% [20 of 81]; P = .014). Multivariate analysis showed that molecular subtype was independently predictive of multifocal and/or multicentric disease.
  
  
  CONCLUSIONS
  Preoperative breast MR imaging is significantly more likely to help detect multifocal and/or multicentric disease and lymph node involvement in luminal B and HER2 molecular subtype breast cancers. Molecular subtype may help to select patients for preoperative breast MR imaging.
authors.affiliation: From the Departments of Radiology (L.J.G., K.S.J., J.A.B., M.S.S.) and Medicine-Oncology (P.K.M.), Duke University Medical Center, 2301 Erwin Rd, Box 3808, Durham, NC 27710.
authors.forename: Lars J
authors.initials: LJ
authors.lastname: Grimm
authors.forename: Karen S
authors.initials: KS
authors.lastname: Johnson
authors.forename: P Kelly
authors.initials: PK
authors.lastname: Marcom
authors.forename: Jay A
authors.initials: JA
authors.lastname: Baker
authors.forename: Mary S
authors.initials: MS
authors.lastname: Soo
mesh_terms: D001943:Breast Neoplasms / Q000145:classification* / Q000175:diagnosis* / Q000235:genetics; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging; D008875:Middle Aged; D018579:Patient Selection; D011300:Preoperative Care; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics; D012189:Retrospective Studies
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human