Neutropenia is the most serious hematologic toxicity of cancer chemotherapy, often limiting the doses of chemotherapy that can be tolerated. Chemotherapy predisposes patients with cancer to infections both by suppressing the production of neutrophils and by cytotoxic effects on the cells that line the alimentary tract. Neutrophils are the first line of defense against infection as the first cellular component of the inflammatory response and a key component of innate immunity. Neutropenic complications associated with myelosuppressive chemotherapy are a significant cause of morbidity and mortality, possibly compromised treatment outcomes, and excessive healthcare costs.

G-CSF is a glycoprotein which stimulates the survival, proliferation, differentiation and function of neutrophil granulocyte progenitor cells and mature neutrophils. The two forms of recombinant human G-CSF in clinical use (filgrastim and pegfilgrastim) are potent stimulants of neutrophil granulopoiesis and are indicated in reduction of duration and incidence of FN in patients treated with cytotoxic chemotherapy for malignancy. Pegfilgrastim is a sustained duration form of filgrastim, due to decreased renal clearance.