title: Local recurrence after breast-conserving therapy in relation to gene expression patterns in a large series of patients.
abstract: OBJECTIVE
  The majority of patients with early-stage breast cancer are treated with breast-conserving therapy (BCT). Several clinical risk factors are associated with local recurrence (LR) after BCT but are unable to explain all instances of LR after BCT. Here, gene expression microarrays are used to identify novel risk factors for LR after BCT.
  
  
  METHODS
  Gene expression profiles of 56 primary invasive breast carcinomas from patients who developed a LR after BCT were compared with profiles of 109 tumors from patients who did not develop a LR after BCT. Both unsupervised and supervised methods of classification were used to separate patients into groups corresponding to disease outcome. In addition, for 15 patients, the gene expression profile in the recurrence was compared with that of the primary tumor.
  
  
  RESULTS
  The two main clusters found by hierarchical cluster analysis of all 165 primary invasive breast carcinomas revealed no association with LR. Predefined gene sets (molecular subtypes and "chromosomal instability" signature) are associated with LR (P = 0.0002 and 0.003, respectively). Significant analysis of microarrays revealed an association between LR and cell proliferation, not captured by histologic grading. Class prediction analysis constructed a gene classifier, which was successfully validated, cross-platform, on an independent data set of 161 patients (log-rank P = 0.041). In multivariate analysis, young age was the only independent predictor of LR.
  
  
  CONCLUSIONS
  We have constructed and cross-platform validated a gene expression profile predictive for LR after BCT, which is characterized by genes involved in cell proliferation but not a surrogate for high histologic grade.
authors.affiliation: Division of Radiation Oncology, The Netherlands Cancer Institute, Amsterdam, the Netherlands.
authors.forename: Bas
authors.initials: B
authors.lastname: Kreike
authors.forename: Hans
authors.initials: H
authors.lastname: Halfwerk
authors.forename: Nicola
authors.initials: N
authors.lastname: Armstrong
authors.forename: Peter
authors.initials: P
authors.lastname: Bult
authors.forename: John A
authors.initials: JA
authors.lastname: Foekens
authors.forename: Sanne C
authors.initials: SC
authors.lastname: Veltkamp
authors.forename: Dimitry S A
authors.initials: DS
authors.lastname: Nuyten
authors.forename: Harry
authors.initials: H
authors.lastname: Bartelink
authors.forename: Marc J
authors.initials: MJ
authors.lastname: van de Vijver
mesh_terms: D000328:Adult; D000367:Age Factors; D001943:Breast Neoplasms / Q000628:therapy*; D016022:Case-Control Studies; D003131:Combined Modality Therapy; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D006801:Humans; D053208:Kaplan-Meier Estimate; D015412:Mastectomy, Segmental; D009364:Neoplasm Recurrence, Local / Q000235:genetics*; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D012307:Risk Factors
chemical_list: D047628:Estrogen Receptor alpha; D018719:Erb-b2 Receptor Tyrosine Kinases; C506487:ESR1 protein, human; C508053:ERBB2 protein, human