Circulating tumor cells in lung cancer: detection methods and clinical applications

Circulating tumor cells (CTCs) are tumor cells that have disseminated from primary and metastatic sites, and circulate in the bloodstream. Advanced immunological and molecular-based methods can be used to detect and analyze the cells with the characteristics of tumor cells, and can be detected and analyzed in the blood of cancer patients. The most commonly used methods in lung cancer combine the processes of immunomagnetic enrichment and immunocytochemical detection, morphology-based enrichment coupled with reverse transcriptase polymerase chain reaction (RT-PCR), and RT-PCR alone. CTC analysis is considered a liquid biopsy approach for early diagnosis, risk stratification, evaluation of curative efficacy, and early detection of lung cancer relapse. In this review, we discuss the present techniques for analyzing CTCs, and the restrictions of using these methods in lung cancer. We also review the clinical studies in lung cancer and discuss the underlying associations between these studies and their future applications to this disease.