title: Correction for chromosome-17 is critical for the determination of true Her-2/neu gene amplification status in breast cancer.
abstract: OBJECTIVE
  Trastuzumab is the cornerstone for treatment of women with HER2-overexpressing breast cancer, both in the adjuvant and in the metastatic settings. The accurate assessment of HER2 is, therefore, critical to identifying patients who may benefit from trastuzumab-based therapy. This project aimed to determine the optimal scoring method for fluorescence in situ hybridization (FISH) assay.
  
  
  METHODS
  FISH assay was done on 893 samples of breast cancer. Three scoring methods were evaluated: Her2/CEP17> or =2, Her2>4, or Her2>6. Protein and gene expression were evaluated by immunohistochemistry (n = 584) and mRNA/assay/nucleic acid sequence-based amplification (NASBA; n = 90).
  
  
  RESULTS
  Samples were divided into five groups based on FISH results: disomic amplified and nonamplified, polysomic amplified, nonamplified, and discordant (10.8% of cases, mostly positive with Her2>4 scoring, but negative with the others). Her2/CEP17> or =2 and Her2>6 scoring methods showed the best association (a) with regard to FISH scoring (kappa = 0.906, P < 10(-6)) and (b) between FISH and immunohistochemistry (3+ as positive; kappa > 0.650, P < 10(-6)) or NASBA (kappa > 0.536, P < 10(-6)). Polysomy had an effect on Her2 copy number (P < 10(-6)), but had no effect on protein and mRNA content. Therefore, within the discordant subgroup, for which additive Her-2 gene copies are due to high polysomy, protein and mRNA levels were similar to those of the nonamplified samples. For this subgroup, the best concordance between FISH/immunohistochemistry/NASBA was observed with the Her2/CEP17 ratio and Her-2>6 scoring (68% and 58% perfect matches, respectively). No perfect matches were observed using the Her2>4 scoring method.
  
  
  CONCLUSIONS
  Correction for chromosome-17 is the method of choice for clinical practice; Her-2>6, but not Her-2>4, could be used as an alternative.
authors.affiliation: Translational Research Unit, Bordet Institute, Brussels, Belgium.
authors.forename: Lissandra
authors.initials: L
authors.lastname: Dal Lago
authors.forename: Virginie
authors.initials: V
authors.lastname: Durbecq
authors.forename: Christine
authors.initials: C
authors.lastname: Desmedt
authors.forename: Roberto
authors.initials: R
authors.lastname: Salgado
authors.forename: Thibault
authors.initials: T
authors.lastname: Verjat
authors.forename: Laurence
authors.initials: L
authors.lastname: Lespagnard
authors.forename: Yan
authors.initials: Y
authors.lastname: Ma
authors.forename: Isabelle
authors.initials: I
authors.lastname: Veys
authors.forename: Angelo
authors.initials: A
authors.lastname: Di Leo
authors.forename: Christos
authors.initials: C
authors.lastname: Sotiriou
authors.forename: Martine
authors.initials: M
authors.lastname: Piccart
authors.forename: Denis
authors.initials: D
authors.lastname: Larsimont
mesh_terms: D000782:Aneuploidy; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism; D002886:Chromosomes, Human, Pair 17 / Q000235:genetics*; D005260:Female; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D021141:Nucleic Acid Amplification Techniques; D012333:RNA, Messenger / Q000096:biosynthesis; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D012333:RNA, Messenger; D018719:Erb-b2 Receptor Tyrosine Kinases