EML4-ALK V3, treatment resistance, and survival: refining the diagnosis of ALK⁺ NSCLC

Anaplastic lymphoma kinase (ALK) gene fusions drive approximately 5% of non-small cell lung cancers (NSCLC) (1). Fluorescence in situ hybridization (FISH) and immunohistochemistry are widely used to identify them based on ALK translocation and ALK overexpression, which are common in all cases and equally predict response to tyrosine kinase inhibitors (TKI) (2). On the other hand, the ALK fusion itself varies among patients.