title: "Liquid biopsy"-ctDNA detection with great potential and challenges.
abstract: Circulating tumor DNA (ctDNA) is now being extensively studied as it is a noninvasive "real-time" biomarker that can provide diagnostic and prognostic information before, during treatment and at progression. These include DNA mutations, epigenetic alterations and other forms of tumor-specific abnormalities such as microsatellite instability (MSI) and loss of heterozygosity (LOH). ctDNA is of great value in the process of cancer treatment. However, up to date, there is no strict standard considering the exact biomarker because the development and progression of cancer is extremely complicated. Also, results of the studies evaluating ctDNA are not consistent due to the different detection methods and processing. The major challenge is still assay sensitivity and specificity for analysis of ctDNA. This review mainly focuses on the tumor specific DNA mutations, epigenetic alterations as well as detecting methods of ctDNA. The advantages and disadvantages will also be discussed.
authors.affiliation: 1 Department of Radiation Oncology, Peking University First Hospital, No.7, Xishiku Str., Xicheng District, Beijing 100034, China ; 2 Department of Radiation Oncology, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029, China ; 3 Department of General Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, 321 Zhongshan Road, Nanjing 210008, China.
authors.forename: Mingwei
authors.initials: M
authors.lastname: Ma
authors.affiliation: 1 Department of Radiation Oncology, Peking University First Hospital, No.7, Xishiku Str., Xicheng District, Beijing 100034, China ; 2 Department of Radiation Oncology, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029, China ; 3 Department of General Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, 321 Zhongshan Road, Nanjing 210008, China.
authors.forename: Hongcheng
authors.initials: H
authors.lastname: Zhu
authors.affiliation: 1 Department of Radiation Oncology, Peking University First Hospital, No.7, Xishiku Str., Xicheng District, Beijing 100034, China ; 2 Department of Radiation Oncology, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029, China ; 3 Department of General Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, 321 Zhongshan Road, Nanjing 210008, China.
authors.forename: Chi
authors.initials: C
authors.lastname: Zhang
authors.affiliation: 1 Department of Radiation Oncology, Peking University First Hospital, No.7, Xishiku Str., Xicheng District, Beijing 100034, China ; 2 Department of Radiation Oncology, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029, China ; 3 Department of General Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, 321 Zhongshan Road, Nanjing 210008, China.
authors.forename: Xinchen
authors.initials: X
authors.lastname: Sun
authors.affiliation: 1 Department of Radiation Oncology, Peking University First Hospital, No.7, Xishiku Str., Xicheng District, Beijing 100034, China ; 2 Department of Radiation Oncology, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029, China ; 3 Department of General Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, 321 Zhongshan Road, Nanjing 210008, China.
authors.forename: Xianshu
authors.initials: X
authors.lastname: Gao
authors.affiliation: 1 Department of Radiation Oncology, Peking University First Hospital, No.7, Xishiku Str., Xicheng District, Beijing 100034, China ; 2 Department of Radiation Oncology, The First Affiliated Hospital, Nanjing Medical University, 300 Guangzhou Road, Nanjing 210029, China ; 3 Department of General Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, 321 Zhongshan Road, Nanjing 210008, China.
authors.forename: Gang
authors.initials: G
authors.lastname: Chen
keywords: Circulating tumor DNA (ctDNA); DNA methylation; DNA mutation; biomarker; cancer