title: Added value of HER-2 amplification testing by multiplex ligation-dependent probe amplification in invasive breast cancer.
abstract: BACKGROUND
  HER-2 is a prognostic and predictive marker, but as yet no technique is perfectly able to identify patients likely to benefit from HER-2 targeted therapies. We aimed to prospectively assess the added value of first-line co-testing by IHC, and multiplex ligation-dependent probe amplification (MLPA) and chromogenic in situ hybridization (CISH).
  
  
  METHODS
  As local validation, HER-2 MLPA and CISH were compared in 99 breast cancers. Next, we reviewed 937 invasive breast cancers, from 4 Dutch pathology laboratories, that were prospectively assessed for HER-2 by IHC and MLPA (and CISH in selected cases).
  
  
  RESULTS
  The validation study demonstrated 100% concordance between CISH and MLPA, if both methods were assessable and conclusive (81.8% of cases). Significant variation regarding percentages IHC 0/1+ and 2+ cases was observed between the laboratories (p<0.0001). Overall concordance between IHC and MLPA/CISH was 98.1% (575/586) (Kappa = 0.94). Of the IHC 3+ cases, 6.7% failed to reveal gene amplification, whereas 0.8% of the IHC 0/1+ cases demonstrated gene amplification. Results remained discordant after retrospective review in 3/11 discordant cases. In the remaining 8 cases the original IHC score was incorrect or adapted after repeated IHC staining.
  
  
  CONCLUSIONS
  MLPA is a low-cost and quantitative high-throughput technique with near perfect concordance with CISH. The use of MLPA in routinely co-testing all breast cancers may reduce HER-2 testing variation between laboratories, may serve as quality control for IHC, will reveal IHC 0/1+ patients with gene amplification, likely responsive to trastuzumab, and identify IHC 3+ cases without gene amplification that may respond less well.
authors: Symbiant Pathology Expert Centre, Alkmaar, The Netherlands.
authors: Chantal C H J
authors: CC
authors: Kuijpers
authors: Cathy B
authors: CB
authors: Moelans
authors: Henk-Jan
authors: HJ
authors: van Slooten
authors: Anja
authors: A
authors: Horstman
authors: John W J
authors: JW
authors: Hinrichs
authors: Shaimaa
authors: S
authors: Al-Janabi
authors: Paul J
authors: PJ
authors: van Diest
authors: Mehdi
authors: M
authors: Jiwa
mesh_terms: D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology*; D005260:Female; D005784:Gene Amplification; D006801:Humans; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D060885:Multiplex Polymerase Chain Reaction / Q000379:methods*; D009361:Neoplasm Invasiveness; D009426:Netherlands; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000235:genetics*; D015203:Reproducibility of Results
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human