Discrepancies between FISH and immunohistochemistry for assessment of the ALK status are associated with ALK ‘borderline’-positive rearrangements or a high copy number: a potential major issue for anti-ALK therapeutic strategies

• Published in: Annals of oncology Vol. 26; no. 1; pp. 238 - 244
• Main Authors: Ilie, M.I., Bence, C., Hofman, V., Long-Mira, E., Butori, C., Bouhlel, L., Lalvée, S., Mouroux, J., Poudenx, M., Otto, J., Marquette, C.H., Hofman, P.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01-01-2015
• Subjects: Adenocarcinoma - drug therapy; Adenocarcinoma - genetics; Adenocarcinoma - mortality; Adenocarcinoma of Lung; Adult; Aged; Aged, 80 and over; ALK; Anaplastic Lymphoma Kinase; Crizotinib; discrepancy; Female; fluorescence in situ hybridization; Fluorescent Antibody Technique - methods; Gene Dosage - genetics; Gene Rearrangement; Genetic Variation - genetics; Humans; immunohistochemistry; In Situ Hybridization, Fluorescence - methods; lung adenocarcinoma; Lung Neoplasms - drug therapy; Lung Neoplasms - genetics; Lung Neoplasms - mortality; Male; Middle Aged; Protein Kinase Inhibitors - therapeutic use; Protein-Tyrosine Kinases - analysis; Proto-Oncogene Proteins - analysis; Proto-Oncogene Proteins c-met - analysis; Proto-Oncogene Proteins c-met - antagonists & inhibitors; Pyrazoles - therapeutic use; Pyridines - therapeutic use; Receptor Protein-Tyrosine Kinases - analysis; Receptor Protein-Tyrosine Kinases - antagonists & inhibitors; Receptor Protein-Tyrosine Kinases - genetics; ALK; fluorescence in situ hybridization; crizotinib; immunohistochemistry; discrepancy; lung adenocarcinoma
• ISSN: 0923-7534; 1569-8041
• DOI: 10.1093/annonc/mdu484

Patients with advanced lung adenocarcinomas expressing ALK rearrangements are highly responsive to crizotinib, a dual ALK/c-MET inhibitor. Immunohistochemistry (IHC) is an easy clinically and routinely applicable cost-effective assay for ALK, c-MET and ROS1 protein expression for potential treatment with crizotinib. The purpose of this study was to evaluate the percentage and the pattern of ALK-rearranged cells, the variation in the native ALK copy number, as well as ALK, c-MET and ROS1 protein expression, and their significance on outcome of crizotinib-treated lung adenocarcinoma patients.
Consecutive lung adenocarcinoma specimens (n = 176) ‘double-negative’ (wild-type EGFR and KRAS) were tested for ALK rearrangements/copy number alterations and for ALK, c-MET and ROS1 protein expression using automated standardized protocols. Preliminary data on the outcome of crizotinib-treated patients were recorded.
FISH analysis identified 26/176 (15%) cases with ALK rearrangements. Seven cases had discordant results between the ALK FISH and IHC. Five cases with discordant FISH-positive/IHC-negative revealed FISH ‘borderline’ positivity (15%–20%). Three cases overexpressed c-MET and responded to crizotinib, and two cases with ALK-‘borderline’ rearranged cells only, not associated with c-MET expression, progressed under crizotinib. Two cases with discordant FISH-negative/IHC-positive revealed ALK gene amplification without associated c-MET or ROS1 protein expression.
The discrepancies observed between the IHC and FISH data revealed unexpected biological events, rather than technical issues, which potentially can have a strong impact on the therapeutic strategy with crizotinib.