Although highly malignant, childhood leukemia responds well to treatment, and children tolerate high-dose chemotherapy significantly better than adults. In recent years, with the emergence of new chemotherapy drugs and the continuous improvement of chemotherapy regimens, the efficacy of childhood leukemia has progressed, with long-term disease-free survival rates (cure rates) reaching over 90% for acute lymphoblastic leukemia and over 70% for acute myeloid leukemia, the key being to receive systematic and regular treatment. At present, the domestic treatment of childhood leukemia is very mature, and in the better experienced hospitals, the efficacy has reached international standards. More than 15,000 children with leukemia are added each year in China, but less than 5% receive formal treatment in rural areas and less than 10% in cities, mainly due to the lack of awareness, most grassroots doctors and parents believe that childhood leukemia is incurable. In recent years, the majority of childhood leukemia specialists have gradually concluded that treatment should be developed according to the risk factors present in the child at the time of onset, response to early treatment, etc. Moreover, individualized treatment is emphasized on the basis of standardized treatment. The goal is to enable the child to survive, but also to have a normal quality of life later. Currently, the main treatment for childhood leukemia is chemotherapy, followed by radiotherapy, hematopoietic stem cell transplantation, biological therapy and immunotherapy. Chemotherapy is administered by intramuscular injection, intravenous injection, intrathecal injection and oral administration of anti-cancer drugs to achieve the purpose of treatment. These drugs enter the blood circulation and reach all parts of the body so that chemotherapy can work on cancers that have spread like leukemia. (A) Leukemia chemotherapy strategy Leukemia treatment emphasizes the combination of multiple drugs, i.e., the combination of drugs selected to act on different aspects of leukemia cell metabolism in order to maximize the killing of leukemia cells. When leukemia is clinically diagnosed, there are already about 1 kg of leukemia cells in the body. When chemotherapy makes leukemia reach complete remission, there are still 10 times 8 to 10 times 10 leukemia cells in the body, and if treatment is not continued, these residual leukemia cells (micro residual disease) proliferate further, which will soon cause relapse. Therefore, the treatment of leukemia emphasizes sequential therapy, i.e., early high-dose multi-drug combination induction therapy to focus on the war of annihilation, continuing consolidation therapy after remission to multiply the success, and then entering the maintenance therapy phase. For high-risk patients, intensive therapy is regularly administered during the maintenance phase, with a general course of 2 years for the low-risk group and 2.5 to 3 years for the high-risk group, and eventually discontinued for observation. (B) Common side effects of chemotherapy and countermeasures chemotherapy drugs can kill leukemia cells and also kill normal blood cells and cells with faster metabolism such as mucous membrane cells, causing infection, bleeding, anemia, ulcers, hair loss, nausea, vomiting and other symptoms, which can be solved by subcutaneous injection of hematopoietic stimulating factor, transfusion of blood cells, anti-infection with antibiotics, gammaglobulin and other antiemetic drugs. Second, intrathecal injection of drugs (sheath injection) because of the existence of the blood-brain barrier, chemotherapy drugs into the blood vessels is difficult to reach the brain, some drugs in large doses can enter the brain tissue through the blood-brain barrier, but the vast majority of chemotherapy drugs is difficult to cross the blood-brain barrier, so that when chemotherapy makes the bone marrow and other parts of the leukemia cells are killed, these cells will escape this killing, hiding in the brain tissue, in the brain tissue form a shelter, and after a certain period of proliferation, a large number of leukemic cells are released into the peripheral blood or into the bone marrow, causing relapse. In addition to intravenous systemic chemotherapy, certain chemotherapeutic drugs are injected into the cerebrospinal fluid through lumbar puncture and brought into the brain tissue through the cerebrospinal fluid circulation to effectively prevent relapse caused by “shelter”. Radiation therapy (radiotherapy) is the use of radiation to treat leukemia. It used to be used for the prevention and treatment of meningeal leukemia and testicular leukemia, but in recent years, it has been found that radiotherapy can lead to delayed growth and development, affect organ function, and produce second tumors. Moreover, brain and spinal cord radiotherapy was often chosen in the past, but now only brain radiotherapy is done and the dose of radiotherapy is significantly reduced compared with the previous one. IV. Hematopoietic stem cell transplantation Hematopoietic stem cell transplantation includes autologous peripheral blood stem cell transplantation, autologous bone marrow stem cell transplantation, allogeneic bone marrow stem cell transplantation, allogeneic peripheral blood stem cell transplantation and cord blood stem cell transplantation. Currently, it is only used in children who are at high risk and who have failed chemotherapy again after relapse. The child is first given high-dose drug combination chemotherapy to obtain remission, and then pretreated so that the blood cells in the child’s body, including leukemia cells, are beaten to 0. Then, hematopoietic stem cells, which are pre-drawn and treated in some way, are imported into the child’s body, and these stem cells will then colonize the bone marrow of the child and gradually proliferate and differentiate into various blood cells, which are released into the peripheral blood to perform their functions. Stem cell transplantation can be a complement to chemotherapy by providing remission or even cure for some refractory and relapsed leukemias. At the time of stem cell transplantation, the child is extremely susceptible to infection because the normal blood cells in the child’s body have hit 0. Therefore, the child is isolated in a sterile laminar flow ward and can be released from the laminar flow ward after 20-30 days when the transplantation is successful and the child’s hematopoietic function is reestablished. In addition, stem cell transplantation also produces graft reaction, which is usually mild and can be safely passed with proper treatment. The best bone marrow source (donor) for allogeneic stem cell transplantation is twin sisters, and monozygotic twins are the best, because this kind of donor transplantation reaction is small and also easy to transplant successfully. V. Immune-targeted therapy leukemia cells express certain markers on their cell membranes, and using these markers some antibodies are prepared that can bind to them. When these antibodies enter the body and bind to leukemia cells, they activate the immune system in the body and target to kill these leukemia cells, such as melphalan can kill B-lymphocyte leukemia. In addition, there are treatments such as interleukins and activated T-killing lymphocytes.