Identification of circulating tumor cells with EML4-ALK translocation using fluorescence in situ hybridization in advanced ALK-positive patients with lung cancer

Analysis of anaplastic lymphoma kinase (ALK) rearrangement in non-small cell lung cancer (NSCLC) is considered to be a useful tool when considering predictive biomarker detection for evaluating eligibility for targeted therapy. It is not always possible to perform a tumor biopsy in patients. Isolation and culturing of circulating tumor cells (CTCs) may be an alternative to tumor biopsies for the diagnosis of ALK rearrangement. Blood was collected from 22 patients with NSCLC harboring ALK rearrangement and was divided into two groups: One for immunofluorescence staining and the other for culture. Samples were filtered by size and cultured CTCs were analyzed for echinoderm microtubule-associated protein-like 4-ALK translocation using fluorescence in situ hybridization. CTCs positive for epithelial cell adhesion molecule and CTCs exhibiting ALK rearrangement were detected. Therefore, CTCs may be used as a potential alternative method to tissue biopsy for diagnosing ALK rearrangement. Additionally, this method may have clinical applications including serial blood sampling for the development of personalized cancer therapy based on individual genomic information.