Discordance between anaplastic lymphoma kinase status in primary non‐small‐cell lung cancers and their corresponding metastases

AIMS: The anaplastic lymphoma kinase gene (ALK) has attracted considerable attention as a potential molecular target in non-small-cell lung cancer (NSCLC). However, it is unclear whether ALK alterations are acquired during the metastatic progression of NSCLC. METHODS AND RESULTS: ALK status and ALK expression were evaluated in a series of 67 primary NSCLCs and their corresponding metastatic lesions using fluorescence in-situ hybridization and immunohistochemistry. ALK rearrangement was detected in 7.5% (5/67) of the primary tumours and in 9.0% (6/67) of the metastases (P < 0.001). ALK copy number gain (CNG) was detected in 1.5% (1/67) of the primary tumours and in 35.8% (24/67) of the metastases. Whereas ALK rearrangement was detected only in adenocarcinomas, CNG was identified in various histological subtypes of NSCLC. ALK expression was detected in 11.9% (8/67) of the primary tumours and in 25.4% (17/67) of the metastatic lesions. CONCLUSIONS: ALK alteration and ALK expression can be acquired during metastatic progression in NSCLC, and ALK CNG is associated with ALK expression.