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The performance of next generation sequencing in profiling somatic mutations from plasma samples, especially in early‐stage cancer, is limited by its sensitivity due to the extremely low amount of cell‐free DNA (cfDNA). Polymerase‐chain reaction amplification of limited amounts of DNA often results in product redundancy and the amplification of contaminant DNA. Numerous methods have been developed to detect and quantify ultralow frequency mutations. In this study, the potential of tagging each DNA molecule with a unique molecular identifier (UMI) is explored to detect ultralow frequency mutations in early‐stage lung cancer patients. Paired tissue and blood samples from 32 patients with early‐stage (stage IA‐IIB) nonsmall cell lung cancer are sequenced using a panel consisting of 168 cancer‐related genes. Collectively, 93.8% of tissue samples and 59.4% of plasma samples have mutations detected. The concordance rates are acceptable for all patients except for stage IA. Notably, mutations at an alleleic frequency as low as 0.1% are detected in UMI‐tagged cfDNA samples. Moreover, patients with nonadenocarcinoma histology have a significantly higher detection rate than patients with adenocarcinoma (92.9% vs 33.3%, P = 0.002). The study demonstrates the potential of UMI in early detection of lung cancer from plasma samples. [ABSTRACT FROM AUTHOR]

Background: Detection of circulating tumor DNA (ctDNA) is a promising method for postoperative surveillance of lung cancer. However, relatively low positive rate in early stage patients restricts its application. Aberrant methylation of ctDNA can be detected in blood samples, and may provide a more sensitive method. This study is designed to systematically evaluate and compare the detection of aberrant methylation and mutations in ctDNA among surgical non-small cell lung cancer (NSCLC) patients, aiming to investigate the feasibility of ctDNA detection as a means of lung cancer surveillance.Methods: This is a prospective observational study. Consecutive surgical NSCLC patients will be recruited. Blood samples will be collected both before and after surgery (during the follow-up period), while matching tumor tissues and tumor-adjacent normal tissues will be collected during surgery. Quantitative analysis of aberrant methylation and mutations of ctDNA will be conducted in combination with a three-year follow-up data.Discussion: This is the first registered prospective study designed to investigate the feasibility of ctDNA methylation detection as a means of postoperative lung cancer surveillance. We will systematically evaluate and compare the quantitative detection of ctDNA mutations and ctDNA methylation in surgical NSCLC patients, combining with the follow-up information. By integrating genetic and epigenetic information of ctDNA, more effective strategies for postoperative surveillance may be defined.Trial Registration: This study (MEDAL, MEthylation based Dynamic Analysis for Lung cancer) was registered on ClinicalTrials.gov on 08/05/2018 (NCT03634826; Pre-results). [ABSTRACT FROM AUTHOR]