An international interpretation study using the ALK IHC antibody D5F3 and a sensitive detection kit demonstrates high concordance between ALK IHC and ALK FISH and between evaluators.
BACKGROUND
The goal of personalized medicine is to treat patients with a therapy predicted to be efficacious based on the molecular characteristics of the tumor, thereby sparing the patient futile or toxic therapy. Anaplastic lymphoma kinase (ALK) inhibitors are effective against ALK-positive non-small-cell lung cancer (NSCLC) tumors, but to date the only 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 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 combined with OptiView DAB IHC detection and OptiView amplification (Ventana Medical Systems, Inc., Tucson, AZ). Specimens were scored binarily as positive if strong granular cytoplasmic brown staining was present in tumor cells. IHC results were compared with the FISH results and interevaluator comparisons made.


RESULTS
Overall for the 100 evaluable cases the ALK IHC assay was highly sensitive (90%), specific (95%), and accurate relative (93%) to the ALK FISH results. Similar results were observed using a majority score. IHC negativity was scored by seven of seven and six of seven evaluators on three and two FISH-positive cases, respectively. IHC positivity was scored on two FISH-negative cases by seven of seven readers. There was agreement among seven of seven and six of seven readers on 88% and 96% of the cases before review, respectively, and after review there was agreement among seven of seven and six of seven on 95% and 97% of the cases, respectively.


CONCLUSIONS
On the basis of expert evaluation the ALK IHC test is sensitive, specific, and accurate, and a majority score of multiple readers does not improve these results over an individual reader's score. Excellent inter-reader agreement was observed. These data support the algorithmic use of ALK IHC in the evaluation of NSCLC.
*Department of Medicine, Division of Medical Oncology, University of Colorado, Aurora, Colorado; †Department of Pathology Brigham and Women's Hospital, Boston, Massachusetts; ‡Institute of Pathology, Charité University Hospital Berlin, Germany; §Department of Pathology and Medical Biology, University of Groningen, University Medical Centre Groningen, The Netherlands; ‖Princess Margaret Hospital, University Health Network, University of Toronto, Ontario, Canada; ¶Department of Pathology and Molecular Diagnostics, Aichi Cancer Center, Kanokoden, Chikusa-ku, Nagoya, Japan; #Pathology and Laboratory Medicine Institute, Cleveland Clinic, Cleveland, Ohio; ** Department of Pathology, University of Colorado, Aurora, Colorado; and ††University of Colorado Comprehensive Cancer Center, Aurora, Colorado.
Murry W
MW
Wynes
Lynette M
LM
Sholl
Manfred
M
Dietel
Ed
E
Schuuring
Ming S
MS
Tsao
Yasushi
Y
Yatabe
Raymond R
RR
Tubbs
Fred R
FR
Hirsch
D000077548:Anaplastic Lymphoma Kinase; D000906:Antibodies; D014408:Biomarkers, Tumor / Q000032:analysis*; D002289:Carcinoma, Non-Small-Cell Lung / Q000737:chemistry*; D005188:False Negative Reactions; D005189:False Positive Reactions; D006801:Humans; D007150:Immunohistochemistry / Q000379:methods; D017404:In Situ Hybridization, Fluorescence; D008175:Lung Neoplasms / Q000737:chemistry*; D015588:Observer Variation; D057285:Precision Medicine; D020794:Receptor Protein-Tyrosine Kinases / Q000032:analysis* / Q000276:immunology; D012680:Sensitivity and Specificity
D000906:Antibodies; D014408:Biomarkers, Tumor; C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; D020794:Receptor Protein-Tyrosine Kinases