Febrile neutropenia is a life-threatening oncologic emergency situation that often requires use of antibiotics and hospitalization and reduces quality of life.4 Filgrastim (recombinant human granulocyte colony stimulating factor (G-CSF)) is used to reduce the incidence of neutropenia associated with bone marrow–suppressing chemotherapy in patients with cancer.5 Here, CSF3 is linked to neutropenia.