Abstract
Lung cancer is one of the most common cancers and the predominant cause of cancer-related death in the world. The low accuracy of early detection techniques and high risk of relapse greatly contribute to poor prognosis. An accurate clinical tool that can assist in diagnosis and surveillance is urgently needed. Circulating tumor DNA (ctDNA) is free DNA shed from tumor cells and isolated from peripheral blood. The genomic profiles of ctDNA have been shown to closely match those of the corresponding tumors. With the development of approaches with high sensitivity and specificity, ctDNA plays a vital role in the management of lung cancer as a result of its reproducible, non-invasive, and easy-to-obtain characteristics. However, most previous studies have focused on advanced lung cancer. Few studies have investigated ctDNA in the early stages of the disease. In this review, we focus on ctDNA obtained from patients in the early stage of lung cancer, provide a summary of the related literature to date, and describe the main approaches to ctDNA and the clinical applications.