title: Intratumoral distribution of EGFR mutations and copy number in metastatic lung cancer, what impact on the initial molecular diagnosis?
abstract: BACKGROUND
  Activating epidermal growth factor receptor (EGFR) mutations characterize a subgroup of non-small-cell lung cancer that benefit from first line EGFR tyrosine kinase inhibitors (EGFR-TKI). However, the existence of polyclonal cell populations may hinder personalized-medicine strategies as patients' screening often depends upon a single tumor-biopsy sample. The purpose of this study is to clarify and to validate in clinical testing conditions the accuracy of EGFR genotyping using different tumor sites and various types of samples (transthoracic, surgical or endoscopic biopsies and cytology specimens).
  
  
  METHODS
  We conducted a retrospective review of 357 consecutive patients addressed for EGFR mutation screening in accordance with the directive of the European Medicines Agency (stage IV NSCLC). Fifty-seven samples were EGFR mutated and 40 had adequate tumor specimens for analysis on multiple spatially separated sites. Ten wild type samples were also analyzed. A total of 153 and 39 tumor fragments, from mutated and non-mutated cases respectively, were generated to analyze tumor heterogeneity or primary-metastatic discordances. After histological review of all fragments, EGFR genotyping was assessed using the routine diagnostic tools: fragment analysis for insertions and deletions and allele specific TaqMan probes for point mutations. EGFR copy number (CN) was evaluated by qPCR using TaqMan probes.
  
  
  RESULTS
  The identification of EGFR mutations was independent of localization within primary tumor, of specimen type and consistent between primary and metastases. At the opposite, for half of the samples, tumor loci showed different EGFR copy number that may affect mutation detection cut-off.
  
  
  CONCLUSIONS
  This is the largest series reporting multiple EGFR testing in Caucasians. It validates the accuracy of EGFR mutation screening from single tumor-biopsy samples before first line EGFR-TKI. The unpredictable variability in EGFR CN and therefore in EGFR wild type/mutant allelic ratio justifies the implementation of sensitive methods to identify patients with EGFR mutated tumors.
authors.forename: Audrey
authors.initials: A
authors.lastname: Mansuet-Lupo
authors.forename: Fouzia
authors.initials: F
authors.lastname: Zouiti
authors.forename: Marco
authors.initials: M
authors.lastname: Alifano
authors.forename: Anne
authors.initials: A
authors.lastname: Tallet
authors.forename: Marie-Christine
authors.initials: MC
authors.lastname: Charpentier
authors.forename: Véronique
authors.initials: V
authors.lastname: Ducruit
authors.forename: Fabrice
authors.initials: F
authors.lastname: Devez
authors.forename: Fanny
authors.initials: F
authors.lastname: Lemaitre
authors.forename: Pierre
authors.initials: P
authors.lastname: Laurent-Puig
authors.forename: Diane
authors.initials: D
authors.lastname: Damotte
authors.affiliation: Université Paris Descartes, Sorbonne, Paris cité, France. helene.blons@parisdescartes.fr.
authors.forename: Hélène
authors.initials: H
authors.lastname: Blons
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D056915:DNA Copy Number Variations; D066246:ErbB Receptors / Q000235:genetics*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009362:Neoplasm Metastasis; D057089:Pathology, Molecular
chemical_list: D066246:ErbB Receptors