title: A comparative clinical evaluation of the assay of serum extracellular domain of HER2 protein using a chemiluminescent immunoassay method in breast cancer patients with or without HER2 protein expression in immunohistochemistry.
abstract: OBJECTIVE
  The human epidermal growth factor receptor type 2 (HER2) protein has been used as a biomarker for breast cancer. A new method based on chemiluminescent immunoassay for measuring the serum levels of the extracellular domain of HER2 protein (sHER2-ECD) has been developed. Its clinical usefulness has not been clearly established. We studied the clinical usefulness of sHER2-ECD in monitoring breast cancer patients.
  
  
  METHODS
  We examined the clinical effectiveness of sHER2-ECD using the ADVIA Centaur XP System in comparison with conventional tumor markers (CA15-3 and CEA) in 148 patients with breast cancer with or without trastuzumab treatment.
  
  
  RESULTS
  The positive rate for sHER2-ECD, CA15-3, and CEA in trastuzumab patients (36) was 25.0%, 19.4%, and 16.7%, and that in non-trastuzumab patients (112) was 20.5%, 22.3%, and 22.3%, respectively. Twenty-three out of 112(20.5%) non-trastuzumab patients were found positive for sHER2-ECD in spite of the negative IHC. Measurement of sHER2-ECD and CA15-3 showed no difference in the expression profile among different clinical stages. During long-term observation in patients negative for HER2 protein by immunohistochemistry, sHER2-ECD was found to be a relatively sensitive indicator of metastasis to distant organs, such as liver and bone, as compared with CA15-3.
  
  
  CONCLUSIONS
  sHER2-ECD testing may be a useful tumor marker for monitoring breast cancer patients, even in those with negative IHC for the HER2 protein.
authors.affiliation: Department of Clinical Laboratory, Tokai University Hospital, Japan. mokuyasu@is.icc.u-tokai.ac.jp
authors.forename: Seiichi
authors.initials: S
authors.lastname: Mokuyasu
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Suzuki
authors.forename: Takayuki
authors.initials: T
authors.lastname: Seto
authors.forename: Hayato
authors.initials: H
authors.lastname: Miyachi
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Tokuda
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D061067:Antibodies, Monoclonal, Humanized / Q000627:therapeutic use; D000970:Antineoplastic Agents / Q000627:therapeutic use; D014408:Biomarkers, Tumor / Q000097:blood*; D001943:Breast Neoplasms / Q000097:blood* / Q000175:diagnosis; D005260:Female; D006801:Humans; D007118:Immunoassay / Q000379:methods*; D007150:Immunohistochemistry / Q000379:methods*; D008163:Luminescent Measurements / Q000379:methods*; D008875:Middle Aged; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000097:blood*; D012680:Sensitivity and Specificity; D000068878:Trastuzumab
chemical_list: D061067:Antibodies, Monoclonal, Humanized; D000970:Antineoplastic Agents; D014408:Biomarkers, Tumor; D018719:Erb-b2 Receptor Tyrosine Kinases; D000068878:Trastuzumab