title: p95-HER2 and trastuzumab resistance in metastatic breast cancer; is immunohistochemistry appropriate?
abstract: OBJECTIVE
  Unraveling the mechanisms underlying the resistance to trastuzumab is important for amending the prognosis of patients with human epidermal growth factor receptor 2 (HER2) positive metastatic breast cancer. Experimentally, it has been shown that p95-HER2 positive breast tumors are resistant to trastuzumab. The aim of this study was to investigate the predictive and prognostic importance of p95-HER2 expression by immunohistochemistry in HER2-positive metastatic breast cancer patients treated with trastuzumab.
  
  
  METHODS
  Only patients who had a histological diagnosis of HER2-positive metastatic breast cancer and who had received first line therapy containing trastuzumab were enrolled in the study. Immunohistochemistry was used to analyze p95-HER2 expression in the tissue blocks of the patients.
  
  
  RESULTS
  The study was performed on 38 patients aged between 30 and 84 years. In 14 patients (36.8%), p95-HER2 was positive, whereas it was negative in the remaining 24 patients (63.2%). There was no significant correlation between p95-HER2 expression and overall survival, response to trastuzumab, and progression-free survival (PFS).
  
  
  CONCLUSIONS
  Unlike previous reports, there was no correlation between the p95-HER2 expression and resistance to trastuzumab. It may be argued that an analysis using immunohistochemistry is inadequate for determining p95- HER2. In order to ascertain whether immunohistochemistry is an appropriate method, studies with larger patient groups are needed.
authors.affiliation: Department of Medical Oncology, Sanliurfa Training and Research Hospital, Sanliurfa, Turkey.
authors.forename: Muharrem
authors.initials: M
authors.lastname: Kocar
authors.forename: Emine
authors.initials: E
authors.lastname: Bozkurtlar
authors.forename: Ferhat
authors.initials: F
authors.lastname: Telli
authors.forename: Fulden
authors.initials: F
authors.lastname: Yumuk
authors.forename: Handan
authors.initials: H
authors.lastname: Kaya
authors.forename: Hande
authors.initials: H
authors.lastname: Kocar
authors.forename: Nazim
authors.initials: N
authors.lastname: Serdar Turhal
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D061067:Antibodies, Monoclonal, Humanized / Q000008:administration & dosage*; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D019008:Drug Resistance, Neoplasm / Q000235:genetics; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D008875:Middle Aged; D009362:Neoplasm Metastasis; D011379:Prognosis; D051567:Proto-Oncogene Proteins c-vav / Q000096:biosynthesis* / Q000235:genetics; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis* / Q000235:genetics; D000068878:Trastuzumab
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D051567:Proto-Oncogene Proteins c-vav; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab; C496618:VAV1 protein, human; C508053:ERBB2 protein, human