Filgrastim Therapy and Left Shift

Clinical Significance and Management

Infectious left shift typically presents with neutropenia, fever, and clinical deterioration, in contrast to the left shift seen in filgrastim-treated patients, which occurs with rising total neutrophil counts and improving clinical status 1
Standard filgrastim dosing is 5 μg/kg/day subcutaneously, continued until ANC reaches 2-3 × 10⁹/L after the expected nadir, as recommended by clinical guidelines from the American Society of Clinical Oncology 2, 3
Therapy should begin 24-72 hours after completion of myelotoxic chemotherapy, according to clinical guidelines from the National Comprehensive Cancer Network 3
The left shift typically appears as neutrophil recovery begins, usually 6-14 days after chemotherapy, and is a expected response to filgrastim therapy 1
If left shift occurs with fever (≥38.0°C), obtain blood and urine cultures and initiate broad-spectrum antibiotics immediately, as recommended by the Infectious Diseases Society of America 1
Absence of fever or clinical signs of infection supports benign etiology of left shift in filgrastim-treated patients, and therapy can be continued as prescribed until target ANC is achieved 1, 3

Clinical trials reported that filgrastim‑related fever is typically grade 1–2 (mild to moderate), and severe febrile complications are rare, indicating that fever is a relatively mild adverse effect of the drug【4】.
Mild fever without additional concerning features does not warrant stopping filgrastim therapy, because the benefit of accelerated neutrophil recovery outweighs this minor side effect【4】.

Comparative studies demonstrated that less frequent dosing schedules of filgrastim (e.g., intermittent or pegylated formulations) are associated with a lower incidence of grade 1–2 fever compared with daily administration, suggesting a dose‑schedule dependence of this adverse effect【4】.

Systematic reviews found that granulocyte‑macrophage colony‑stimulating factor (GM‑CSF) regimens produce a higher incidence of fever than filgrastim (G‑CSF) regimens, confirming that filgrastim can cause fever but does so less frequently than alternative CSFs【5】.