title: Markers for EGFR pathway activation as predictor of outcome in metastatic colorectal cancer patients treated with or without cetuximab.
abstract: BACKGROUND
  Anti-EGFR monoclonal antibodies in metastatic colorectal cancer (mCRC) treatment are only effective in patients with KRAS wild type tumours. Here we assess the predictive value of other potential relevant markers involved in the epidermal growth factor receptor (EGFR) signalling pathways for response to cetuximab-based treatment.
  
  
  METHODS
  Formalin-fixed paraffin-embedded colorectal cancer tissue of the primary tumour was obtained from 559 mCRC patients treated with chemotherapy and bevacizumab with or without cetuximab (phase III CAIRO2 study). DNA was isolated for mutation analysis of BRAF (V600E), KRAS (codon 12 and 13) and PIK3CA (exon 9 and 20). Tissue microarray's (TMA's) were constructed for the assessment of EGFR and HER2 gene copy number (GCN), and EGFR and PTEN protein expression. The results of these markers, individually or in combination, were correlated with progression-free survival (PFS) and overall survival (OS) in the subgroup of patients with a KRAS wild type tumour treated in the cetuximab-arm. KRAS wild type patients treated without cetuximab were used as a control group.
  
  
  RESULTS
  A total of 208 tumours (39.4%) contained a KRAS mutation, 8.7% a BRAF mutation and 9.9% a PIK3CA mutation. Loss of PTEN expression and the presence EGFR protein expression were observed in 42.0% and 61.7% of the samples, respectively. An increased EGFR GCN was observed in 15.3% of the samples, and 11.5% of the evaluable samples contained an increased HER2 GCN. In KRAS wild type patients treated with cetuximab a BRAF mutation was significantly and independently associated with PFS and OS. In patients treated without cetuximab the PFS and OS were also associated with the BRAF genotype. No prognostic or predictive value was observed for any of the other markers when tested individually or in combination.
  
  
  CONCLUSIONS
  BRAF genotype is correlated with PFS and OS in KRAS wild type mCRC patients, which is independent of cetuximab treatment. PIK3CA mutation, loss of PTEN expression, EGFR GCN and HER2 GCN have no predictive value for response to treatment with cetuximab, neither individually nor in combination with other markers.
authors.affiliation: Department of Medical Oncology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands.
authors.forename: Jolien
authors.initials: J
authors.lastname: Tol
authors.forename: Jeroen R
authors.initials: JR
authors.lastname: Dijkstra
authors.forename: Marjolein
authors.initials: M
authors.lastname: Klomp
authors.forename: Steven
authors.initials: S
authors.lastname: Teerenstra
authors.forename: Martin
authors.initials: M
authors.lastname: Dommerholt
authors.forename: M Elisa
authors.initials: ME
authors.lastname: Vink-Börger
authors.forename: Patricia H
authors.initials: PH
authors.lastname: van Cleef
authors.forename: J Han
authors.initials: JH
authors.lastname: van Krieken
authors.forename: Cornelis J A
authors.initials: CJ
authors.lastname: Punt
authors.forename: Iris D
authors.initials: ID
authors.lastname: Nagtegaal
mesh_terms: D000911:Antibodies, Monoclonal / Q000627:therapeutic use*; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents / Q000627:therapeutic use*; D014408:Biomarkers, Tumor / Q000235:genetics / Q000378:metabolism; D000068818:Cetuximab; D058534:Class I Phosphatidylinositol 3-Kinases; D015179:Colorectal Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D066246:ErbB Receptors / Q000378:metabolism*; D005260:Female; D052138:Genes, Neoplasm / Q000235:genetics*; D018734:Genes, erbB-2 / Q000235:genetics; D011905:Genes, ras / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D008297:Male; D008875:Middle Aged; D009154:Mutation / Q000235:genetics; D009363:Neoplasm Proteins / Q000378:metabolism*; D051059:PTEN Phosphohydrolase / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D048493:Proto-Oncogene Proteins B-raf / Q000378:metabolism; D016283:Proto-Oncogene Proteins p21(ras); D016896:Treatment Outcome; D018631:ras Proteins / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; C117307:KRAS protein, human; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins; D019869:Phosphatidylinositol 3-Kinases; D058534:Class I Phosphatidylinositol 3-Kinases; C484760:PIK3CA protein, human; D066246:ErbB Receptors; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf; D051059:PTEN Phosphohydrolase; C494929:PTEN protein, human; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; D000068818:Cetuximab