Febrile Neutropenia — Fever with low white blood cells

Febrile neutropenia is formally defined as an oral temperature exceeding 38.3°C (or a sustained temperature of 38.0°C over one hour) in a patient whose absolute neutrophil count (ANC) is below 500 cells per microlitre, or expected to fall below 500 cells per microlitre within 48 hours. Neutrophils are white blood cells responsible for clearing microbial pathogens.

Chemotherapy and other anti-cancer drugs damage rapidly dividing haematopoietic stem cells in the bone marrow, triggering a profound, temporary decline in neutrophil production. Without adequate neutrophils, the typical inflammatory signs of infection, such as pus formation, swelling, or redness, may be entirely absent, meaning fever is frequently the sole warning sign of a dangerous bacterial or fungal infection.

This condition demands immediate action because untreated infections can escalate into septic shock, organ failure, or death within hours. Patients receiving cytotoxic therapy must monitor their temperature vigilantly and contact emergency oncology services at the first sign of fever. Recognising febrile neutropenia rapidly enables immediate blood cultures and the prompt start of broad-spectrum antibiotics. Preventing or swiftly resolving these episodes also avoids prolonged hospitalisations and dangerous delays in scheduled cancer treatments, preserving overall clinical outcomes.

Diagnosis requires urgent diagnostic laboratory testing alongside clinical assessment. A full blood count with differential confirms the absolute neutrophil count. Blood samples are drawn from peripheral veins and central venous catheters for microbial culture. Clinicians also order serum creatinine, urea, liver enzymes, and C-reactive protein. Chest radiography, urine cultures, and respiratory viral swabs are frequently conducted to identify the source of infection.

Febrile neutropenia most frequently develops in patients undergoing intensive chemotherapy for haematological malignancies, including acute myeloid leukaemia, acute lymphoblastic leukaemia, and aggressive non-Hodgkin lymphomas. It also regularly occurs during treatment for solid tumours managed with high-dose myelosuppressive regimens, such as breast cancer, ovarian cancer, small cell lung cancer, and soft tissue sarcomas.

Febrile neutropenia requires immediate empirical broad-spectrum intravenous antibiotic therapy, ideally administered within one hour of hospital arrival. High-risk patients remain hospitalised for ongoing monitoring, while selected low-risk patients may transition to outpatient oral regimens. Granulocyte colony-stimulating factors (G-CSF) may be given therapeutically or added prophylactically to subsequent chemotherapy cycles to stimulate bone marrow recovery and prevent recurrence.