Monitoring and Characterization of Circulating Tumor Cells (CTCs) in a Patient With EML4-ALK-Positive Non-Small Cell Lung Cancer (NSCLC)

Circulating tumor cells (CTCs) are epithelial cells that originate from primary tumor and are detectable at a low rate (typically 1 to 1000 per 7.5 mL) in the peripheral blood of patients with cancer; CTCs might settle down at distant sites to give metastasis. The presence of CTCs has been associated with worst prognosis in metastatic cancer of breast, prostate, and colon. Recent experiences demonstrated that CTC detection could help improve diagnosis and predict prognosis in patients with non-small cell lung cancer (NSCLC); however, few data exist in the literature on this topic in patients with EML4-ALK-positive (EML4-ALK(+)) NSCLC. We report a case of a patient with EML4-ALK(+) NSCLC who underwent sequential monitoring and EML4-ALK characterization of CTCs during targeted therapy. We were able to document that the levels of EML4-ALK(+) CTCs reflect the response to crizotinib therapy or ongoing resistance to EML4-ALK inhibitors. We obtained for the first time the proof of principle that our quantitative assay can longitudinally monitor EML4-ALK expression in CTCs under selective pressure of a specific treatment. After demonstrating its clinical utility, in the future we will use it to predict treatment efficacy and to detect early drug resistance to ALK inhibitors. (C) 2016 Elsevier Inc. All rights reserved.