Telpegfilgrastim vs Filgrastim for Secondary Prevention of Chemotherapy-Induced Neutropenia in Pediatric Solid Tumors

Inclusion Criteria: 1. Histologically or cytologically confirmed malignant solid tumor requiring high-intensity chemotherapy, with ≥2 remaining chemotherapy cycles, and either: * Previous febrile neutropenia(FN) or dose-limiting neutropenia in the prior chemotherapy cycle without prophylactic granulocyte colony-stimulating factor (G-CSF); * Previous FN or dose-limiting neutropenia in the prior chemotherapy cycle despite prophylactic G-CSF. 2. Age ≥6 to ≤24 years. 3. Eastern Cooperative Oncology Group Performance Status ≤1. 4. Normal bone marrow hematopoietic function: hemoglobin ≥75 g/L, white blood cell count ≥3.0×10\^9/L, platelets ≥80×10\^9/L, and neutrophils ≥1.5×10\^9/L. 5. Anticipated survival ≥8 months. 6. Willing to participate, with written informed consent signed by the patient or legal guardian. Exclusion Criteria: 1. Bone marrow involvement at screening. 2. Uncontrolled localized or systemic infection. 3. Known hypersensitivity to Telpegfilgrastim, recombinant human granulocyte-colony stimulating factor(rhG-CSF), or other pegylated recombinant human granulocyte colony stimulating factor(PEG-rhG-CSF) agents. 4. Concurrent participation in any other investigational drug or device trial. 5. Severe organ dysfunction: total bilirubin, alanine aminotransferase(ALT), or aspartate transaminase(AST) \>2.5 × upper limit of normal(ULN) (or \>5 × ULN in patients with liver metastases), serum creatinine \>5 × ULN. 6. Severe psychiatric disorders affecting informed consent provision or adverse event assessment. 7. Any condition deemed by the investigator to compromise patient safety or interfere with study outcomes, including risks from the investigational product or confounding adverse event evaluation.