Detection of circulating tumor DNAs(ct DNAs) in cancer patients is an important component of cancer precision medicine ct DNAs. Compared to the traditional physical and biochemical methods, blood-based ct DNA detection offers a non-invasive and easily accessible way for cancer diagnosis, prognostic determination, and guidance for treatment. While studies on this topic are currently underway, clinical translation of ct DNA detection in various types of cancers has been attracting much attention, due to the great potential of ct DNA as blood-based biomarkers for early diagnosis and treatment of cancers. ct DNAs are detected and tracked primarily based on tumorrelated genetic and epigenetic alterations. In this article, we reviewed the available studies on ct DNA detection and described the representative methods. We also discussed the current understanding of ct DNAs in cancer patients and their availability as potential biomarkers for clinical purposes. Considering the progress made and challenges involved in accurate detection of specific cell-free nucleic acids, ct DNAs hold promise to serve as biomarkers for cancer patients, and further validation is needed prior to their broad clinical use. Detection to circulating tumor DNAs (ct DNAs) in cancer patients is an important component of cancer precision medicine ct DNAs. Compared to the traditional physical and biochemical methods, blood-based ct DNA detection offers a non-invasive and accessible accessible for cancer diagnosis , prognostic determination, and guidance for treatment. While studies on this topic are currently underway, clinical translation of ct DNA detection in various types of cancers has been attracting much attention, due to the great potential of ct DNA as blood-based biomarkers for early diagnosis and treatment of cancers. ct DNAs are detected and tracked primarily based on tumorrelated genetic and epigenetic alterations. In this article, we reviewed the available studies on ct DNA detection and described the representative methods. We also discussed the current understanding of ct DNAs in cancer patients and their availability as potential biomarkers for clinical purposes. Considering the progress made and challenges involved in accurate detection of specific cell-free nucleic acids, ct DNAs hold promise to serve as biomarkers for cancer patients, and further validation is needed prior to their broad clinical use.