Comprehensive Review of Febrile Neutropenia
Febrile neutropenia ($\text{FN}$) is a potentially life-threatening complication, most commonly seen in patients undergoing cytotoxic chemotherapy, defined by the presence of fever (a single temperature of $\ge 38.3^\circ\text{C}$ or $\ge 38.0^\circ\text{C}$ sustained for over an hour) concurrently with an abnormally low absolute neutrophil count (ANC, often $
The condition represents a true medical emergency because the immune system is severely compromised, lacking the capacity to mount a robust defense against typically harmless pathogens, allowing for a rapidly progressing and overwhelming infection that can quickly lead to septic shock and multi-organ failure if not promptly managed.
The pathophysiology is rooted in the destruction of rapidly dividing bone marrow cells by chemotherapy, leading to neutropenia, which eliminates the body's first line of defense against bacterial and fungal invasion. The most common source of infection is the patient's own endogenous flora from mucosal surfaces (gut, skin) damaged by the chemotherapy (mucositis). Initial management is time-critical and involves immediate, broad-spectrum, intravenous empiric antibiotic therapy, ideally administered within the first hour of presentation, even before the source of infection is identified. The choice of antibiotics is guided by patient risk stratification, often using validated scores like the Multinational Association for Supportive Care in Cancer ($\text{MASCC}$) risk-index score. High-risk patients typically require hospitalization and combination intravenous therapy covering Pseudomonas aeruginosa, while select low-risk patients may be managed with oral antibiotics in an outpatient setting after the first dose. Prophylaxis is a key supportive measure, primarily involving the use of granulocyte colony-stimulating factors ($\text{G-CSFs}$) to stimulate neutrophil production and shorten the duration of neutropenia in patients receiving highly myelosuppressive regimens, significantly reducing the incidence and severity of $\text{FN}$.