Cancer is an important disease that threatens human health, and the early screening of cancer is of great significance to the prevention and treatment of cancer. Here we introduce a new method for sequencing the cancer's early screening and differentiation, published in Nature, is titled Sensitive tumor detection and classification using plasma cell-free DNA methylmes.

At present, the gold standard for tumor diagnosis and treatment is tumor tissue biopsy. But with further research on tumors, scientists have found that the gold standard is not perfect and has some limitations. For example, because of the dynamic changes of the tumor, the tissue biopsy of the first diagnosis may not reflect the current tumor condition (with a certain lag); the local sampling may not reflect the whole body carcinogenesis; the tissue biopsy is invasive, there will be a variety of potential complications, repeated sampling is limited, and so on.

1.Fluid biopsy can make up for tissue biopsy

With the development of science and technology, the technique of non-invasive liquid biopsy, which can be sampled repeatedly at different time points, has been developed rapidly, because it can make up for the deficiency of tissue biopsy, which makes the research of its application in cancer detection more and more, so it is concerned. （Notice: Because liquid biopsy cannot provide important information for pathological diagnosis and protein expression test, it cannot replace tissue biopsy at present）

2.Bottleneck of conventional fluid biopsy in early cancer detection

The main subject of liquid biopsy was plasma free DNA (cfdna). cfDNA is a small fragment of DNA other than the cellular component of the blood. It is released into the blood after apoptosis or necrosis. The cfDNA content in blood of healthy people is very small, while in cancer patients blood significantly increased. Circulating tumor DNA (ctDNA) is the DNA released into the blood by tumor cells and is part of cfDNA.