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E. Schuuring



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    O04 - Molecular Pathology I (ID 126)

    • Event: WCLC 2013
    • Type: Oral Abstract Session
    • Track: Pathology
    • Presentations: 1
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      O04.06 - An international standardization study using the ALK IHC antibody D5F3 and a sensitive detection kit demonstrates high concordance between ALK IHC and ALK FISH and between evaluators (ID 2875)

      11:25 - 11:35  |  Author(s): E. Schuuring

      • Abstract
      • Presentation
      • Slides

      Background
      The goal of personalized medicine is treating patients with a therapy predicted to be efficacious based on the molecular characteristics of the tumor, thereby sparing the patient futile or detrimental therapy. Anaplastic lymphoma kinase (ALK) inhibitors are effective against ALK positive non-small cell lung cancer (NSCLC) tumors, but to date the only US Food and Drug Administration approved companion diagnostic is a break-apart fluorescence in situ hybridization (FISH) assay. Immunohistochemistry (IHC) is a clinically applicable cost-effective test that is sensitive and specific for ALK protein expression. The purpose of this study was to assemble an international team of expert pathologists to evaluate and standardize the interpretation of a new automated standardized ALK IHC assay.

      Methods
      Archival NSCLC tumor specimens (n=103) previously tested for ALK rearrangement by FISH were provided by the international collaborators. These specimens were stained by IHC with the anti-ALK (D5F3) primary antibody (Ventana Medical Systems, Inc) combined with OptiView DAB IHC detection and OptiView amplification (Ventana Medical Systems, Inc). The evaluators went through an interpretation training session and scored the specimens as positive, if strong granular cytoplasmic brown staining was present in tumor cells, or negative. IHC results were compared to the FISH results and inter-evaluator agreement comparisons made.

      Results
      Overall for the 100 evaluable cases the ALK IHC assay was highly sensitive (90%), specific (95%) and accurate (93%) relative to the ALK FISH results. Similar results were observed using a majority score. For the discrepant cases IHC negativity was scored by 7/7 on 3 FISH positive cases and 6/7 evaluators on 2 additional FISH positive cases. IHC positivity was scored on 2 FISH negative cases by 7/7 readers. There was agreement among 7/7 and 6/7 readers on 88% and 96%% of the cases before a consensus review, respectively, and following a review there was agreement among 7/7 and 6/7 on 95% and 97% of the cases, respectively.

      Conclusion
      Based on expert evaluation the ALK IHC assay using the D5F3 antibody combined with Optiview Detction and Optiview amplification is sensitive, specific and accurate, relative to FISH, and a majority score of multiple readers does not improve these results over an individual reader’s score. Excellent inter-reader agreement was observed for the IHC assay. These data support the algorithmic use of ALK IHC as a screening procedure for ALK protein expression in NSCLC.

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