Abstract
When somatic cells in the human body undergo apoptosis or necrosis, the released DNA enters the bloodstream. This type of DNA is called cell-free DNA (cfDNA). In patients with cancer, DNA released from tumor cells is called circulating tumor DNA (ctDNA), which carries genetic alterations specific to tumor cells. In recent years, ctDNA has attracted particular attention in terms of the concept of liquid biopsy in cancer care. Conventionally, tissue biopsy is required for the definitive diagnosis of cancer, and imaging examinations, such as CT, are performed for evaluating recurrence and residual lesions. Although the treatment burden on cancer patients is being slightly reduced due to advances in medicine, invasive examinations and medical exposure are still unavoidable. In addition, the prognosis of cancer varies considerably depending on the degree of progression at the time of detection. Therefore, the early detection of cancer is of utmost importance. With the increase in health consciousness, more people undergo regular health checkups, and it becomes necessary to diagnose cancer in a larger number of patients at an earlier stage. Although the accuracy of early detection has been improved by new imaging tests and examination techniques, each organ must be examined separately, and some organs are more difficult to examine than others in a regular health checkup. The process of cancer screening, diagnosis, and detection of recurrence after treatment is extensive. It can also be expensive, and some of the examinations may be invasive. If all of these processes can be replaced by the analysis of ctDNA in liquid biopsy, only a single blood sample is required. Under these circumstances, various studies are currently in progress on the use of ctDNA in clinical practice as an approach that may greatly reduce such burden. We present an overview of the current situation of ctDNA, as well as its future issues and prospects.
Highlights
The first report on cell-free DNA (cfDNA) in human blood was made by Mandel and Métais in 1948 [1].in 1998, the presence of DNA originating from the fetus in pregnant women’s blood was discovered [2]
As this mutation was identical to the KRAS mutation detected in the tumor tissue from the same patients [7], it was confirmed that the DNA mutation in the plasma was tumor-derived, and the term “circulating tumor DNA”
These findings indicate that circulating tumor DNA (ctDNA) is evaluable in cancers of unknown primary origin, and the analysis of these mutations showed the possibility of treatment with molecular-targeted drugs
Summary
The first report on cfDNA in human blood was made by Mandel and Métais in 1948 [1]. in 1998, the presence of DNA originating from the fetus in pregnant women’s blood was discovered [2]. In 1989, Stroun, M., et al discovered a cfDNA fraction derived from cancer among fractions of cfDNA in the plasma of cancer patients This was the first report of ctDNA [5,6]. In 1994, the KRAS mutation was identified in plasma cfDNA from pancreatic cancer patients by the PCR method As this mutation was identical to the KRAS mutation detected in the tumor tissue from the same patients [7], it was confirmed that the DNA mutation in the plasma was tumor-derived, and the term “circulating tumor DNA (ctDNA)”. Various clinical studies are in progress, and many of them require biopsy for accurate evaluation In these studies, if biopsy can be replaced with ctDNA assay, the burden on patients will be greatly reduced
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