Chemotherapy and radiotherapy are important methods to treat malignant tumors. Many patients often experience neutropenia or leukopenia after chemotherapy or radiotherapy, in addition to gastrointestinal symptoms such as nausea and vomiting. Neutropenia is sometimes fatal, and the authors once encountered a case of neutrophil deficiency with fever in a patient who died from Pseudomonas aeruginosa infection; therefore, FN should be given high priority. Neutrophils have an important immune function, and if there are too few neutrophils, the patient is susceptible to bacterial and viral infections. Neutrophil deficiency is defined as neutrophil count. fn is defined as oral temperature >38.3°C or 38.0°C for 1 hour accompanied by neutrophil count <0.5×109/L. FN is the most serious toxic side effect of chemotherapy with a mortality rate of 5-20%. in 2013, Thailand reported 14% mortality among 5,809 cancer patients hospitalized with FN. The sites of infection are commonly the gastrointestinal tract (oral cavity, pharynx, esophagus, intestine), sinuses, lungs and skin. Risk factors for the occurrence of FN: 1. elderly patients, especially >65 years; 2. previous radiotherapy or chemotherapy; 3. previous neutropenia or tumor involvement of the bone marrow; 4. previous neutropenia (<500/mcl or <1000/mc but <500/mc expected after 48 hours), infection or open wound, recent surgery; 5. general condition Poor; 6. Liver and kidney dysfunction. FN is an oncology emergency that requires urgent treatment, and antibiotics are the top priority for treating FN, and the concept of 1-2 hours of golden antibiotic use has been proposed. Therefore, patients with neutrophil deficiency should be empirically administered broad-spectrum antibiotics within 1-2 hours at the first sign of infection (e.g., fever). Prophylactic antibiotics should also be administered to neutrophil deficient patients without fever, and a 2012 meta-analysis showed that prophylactic antibiotics significantly reduced mortality in this group of patients. The 2010 IDSA guidelines (latest version) recommend prophylactic use of CSF for patients at high risk of expected FN (≥20% probability); for patients with established FN, prophylactic use of CSF is generally not recommended. The so-called prophylactic use of CSF is defined as the subcutaneous or intravenous administration of CSF 5ug/kg/day 24-72 hours after the end of the last day of chemotherapy.