Low-Dose Liposomal Amphotericin B for Invasive Fungal Infection Prophylaxis in Neutropenic Children

This is a single-center, single-arm, observational clinical study evaluating the efficacy and safety of low-dose liposomal amphotericin B (1 mg/kg/day, intravenous, once daily) for the prevention of invasive fungal infections in children aged 3-17 years with hematological malignancies who develop prolonged neutropenia (absolute neutrophil count ≤ 0.5×10\^9/L, expected to last \> 7 days) and are at high risk for invasive fungal disease. Participants are those who, per the treating physician's routine clinical decision, have been initiated on liposomal amphotericin B prophylaxis at 1 mg/kg/day due to intolerance or toxicity to other antifungal agents. The primary outcome is the incidence of proven or probable invasive fungal disease. Secondary outcomes include incidence of pneumonia, persistent unexplained fever \>4 days, use of additional systemic antifungal therapy, and adverse events. A total of 30 participants will be enrolled. Data will be collected at baseline, during treatment, and within 7 days after treatment completion.

Inclusion Criteria: * Age 3 to 17 years (inclusive), both sexes. * Meets NCCN 2025 V1 guideline criteria for high-risk invasive fungal disease, including allogeneic hematopoietic stem cell transplantation, autologous hematopoietic cell transplantation with mucosal damage, acute leukemia, grade 3/4 graft-versus-host disease, myelodysplastic syndrome, lymphoma(a), multiple myeloma(a), chronic lymphocytic leukemia(a), treatment with purine analogues (fludarabine, clofarabine, nelarabine), chimeric antigen receptor (CAR) T-cell therapy, alemtuzumab therapy, with expected neutropenia \>7 days(b) and accompanied by agranulocytosis. Note (a): For these heterogeneous diseases, myeloablative therapy must be met; if neutropenia \>7 days is not met, the patient should be excluded. Note (b): Agranulocytosis is defined as absolute neutrophil count ≤0.5×10\^9/L, or absolute neutrophil count ≤1×10\^9/L with expected decline to ≤0.5×10\^9/L within 48 hours. * Assessed by the study physician as having high-risk for invasive fungal infection, intolerant or unable to use other antifungal agents due to toxicity or other reasons, and the treating physician has independently decided in routine clinical practice to initiate liposomal amphotericin B for antifungal prophylaxis for 3-5 days, with the selected dosage regimen of 1 mg/kg/day, intravenous, once daily. * Patient or legally authorized representative has voluntarily signed the informed consent form. Exclusion Criteria: * Allergy to any component of liposomal amphotericin B, or development of serious adverse events during the initial 3-5 days of prophylactic use. * Prior history of proven or probable invasive fungal disease (IFD). * Presence of pneumonia, unexplained fever, or clinical/imaging evidence suggestive of or diagnosed as fungal infection during screening. * Clinically significant hypokalemia (defined as serum potassium \