Tumor markers were introduced by Herberman at the Conference on Human Immunity and Tumor Immunodiagnosis held at the National Cancer Institute in 1978, and were recognized as a special term at the 7th Conference on the Biology and Medicine of Oncogenesis in the United Kingdom in 1979. Over the past thirty years, the study of tumor markers has gradually formed an independent branch of discipline. Tumor markers are substances that are biosynthesized and released by tumor cells or produced by the body in response to tumor cells during the process of tumorigenesis and proliferation, and these substances can exist in tumor cells and tissues or enter the blood and other body fluids. When tumors develop, these substances are obviously abnormal and can be detected qualitatively or quantitatively using biochemical, immunological and molecular biology techniques. The serum levels of tumor markers generally have good correlation with the occurrence, development, regression and recurrence of malignant tumors. Therefore, the determination of serum tumor marker levels can obtain information about the diagnosis, efficacy and prognosis of malignant tumors. I. Screening for high-risk groups Early detection, early diagnosis and early treatment are the important principles of tumor diagnosis and treatment. It is generally believed that tumors of 1~1.5cm in diameter can be detected by modern biophysical techniques such as ultrasound imaging, computed tomography and magnetic resonance imaging, while tumors growing to 2~3mm can be measured by immunological diagnostic methods. Tumor marker testing is an important clue to detect asymptomatic patients and can be used as an auxiliary diagnostic tool for tumors. Among all the markers, only AFP and PSA can be used for screening, such as AFP test for chronic hepatitis B virus carriers, chronic hepatitis B and hepatitis C patients, which can detect liver cancer at an early stage; PSA combined with rectal examination is also widely used for early prostate cancer screening around the world. Differential diagnosis and clinical staging of tumors After sufficient clinical evidence has been obtained to prove that a patient may have a certain organ tumor, tumor markers can often provide useful information to help distinguish benign and malignant tumors and tumor types, for example, CEA and NSE can help distinguish whether a gastrointestinal tumor is an adenocarcinoma (CEA positive, NSE negative) or a carcinoid tumor (CEA negative, NSE positive); elevated levels of serum tumor markers are associated with tumor size and classification. The level of serum tumor markers is related to the size and differentiation of tumor, and their quantitative detection can help to assist in the diagnosis of clinical stage. The dynamic monitoring of tumor markers can help to determine whether the tumor is recurrent. It is generally recommended that the first measurement should be made in the 6th week after treatment, once every 3 months in the first 3 years, once every 6 months in 3~5 years, and once every year in 5~7 years. If the tumor marker is found to be elevated (25% higher than the first value), it should be measured once again after 2~4 weeks. 2 consecutive elevations are indicative of recurrence or metastasis. Newlands et al. reported that HCG and AFP could be used as prognostic indicators for testicular cancer, and the 4-year survival rate for HCG <50u hcg="">50U/L or AFP >500U/L was 56%. In addition, the changes of CEA concentration in colon cancer, β2 microglobulin concentration in non-Hodgkin’s lymphoma and CA125 concentration in ovarian cancer have prognostic value. Tumor efficacy testing Tumor markers help to clarify whether surgery, radiotherapy or drug treatment is effective. Usually, after successful treatment such as complete resection of tumor and effective chemotherapy, tumor markers will drop significantly, and treatment is considered successful if it drops to normal or 95% of the pre-treatment level; if tumor markers do not drop as expected after surgery, it means that the surgery failed to remove the tumor successfully. The time of tumor marker decline depends on the half-life of tumor markers, Table 1 shows the half-life of common tumor markers. V. Combined detection of tumor markers One tumor can produce multiple tumor markers, different tumors or different tissue types of the same tumor can have the same tumor markers, and the quality and quantity of tumor markers in different tumor patients vary greatly. Since most of the individual tumor markers have low sensitivity or specificity and cannot meet the clinical needs, in recent decade, theoretically and practically, multiple tumor markers are advocated to be measured simultaneously to improve sensitivity and specificity, but the indexes of joint testing must be scientifically analyzed and strictly screened, under this premise, 3~5 tumor markers with high sensitivity and specificity are reasonably selected for joint testing, which can avoid The combination of commonly used tumor markers can be used to avoid the waste of medical resources and reduce the economic burden of patients. The combination of commonly used tumor markers. The so-called “individualized medical treatment” refers to the use of appropriate route of drug administration and the administration of appropriate drugs and appropriate doses to appropriate patients at appropriate treatment time, in order to avoid inappropriate treatment and harmful treatment and reduce toxic side effects of drugs. The identification of individual patient differences is based on certain specific molecular markers (targets), and achieving accurate detection and evaluation of multiple these targets is the basis of individualized medical treatment for tumors. With the discovery of new targeted drugs and in-depth research, the target detection of individualized medicine will also develop from single target detection to multi-target combined detection, and finally form a target detection system, which is expected to improve the targeting and effectiveness of targeted therapy.