Risk of hospitalization for neutropenic complications of chemotherapy in patients with primary solid tumors receiving pegfilgrastim or filgrastim prophylaxis: a retrospective cohort study.

BACKGROUND: In a meta-analysis of data from randomized trials, the risk of febrile neutropenia during myelosuppressive chemotherapy was reported to be lower with pegfilgrastim prophylaxis than filgrastim prophylaxis. However, there is limited information on the comparative effectiveness of these agents in clinical practice.
OBJECTIVE: This study was undertaken to compare the risks of hospitalization for neutropenic complications of chemotherapy in US clinical practice in patients with primary solid tumors receiving pegfilgrastim or filgrastim prophylaxis.
METHODS: This was a retrospective cohort study employing a US health insurance database. The source population included all patients who received chemotherapy for a primary solid tumor between January 2003 and December 2005 and who received filgrastim or pegfilgrastim during their first course of chemotherapy. All unique chemotherapy cycles were identified for each patient, and cycles in which pegfilgrastim or filgrastim was administered by cycle day 5 (considered to represent prophylaxis) were selected and pooled for analysis. The risks of hospitalization for neutro-penic complications (using both narrow and broad criteria) and for any reason were then compared between cycles in which filgrastim or pegfilgrastim prophylaxis was administered. Generalized estimating equations were used to control for potential confounding variables.
RESULTS: Filgrastim prophylaxis was used in 1193 unique chemotherapy cycles (mean [SD] number of days per cycle, 4.5 [3.3]); for pegfilgrastim prophylaxis, the number of unique chemotherapy cycles was 14,570. First-cycle use represented 16% of all cycles analyzed. The mean ages of patients receiving filgrastim and pegfilgrastim prophylaxis were 61 and 60 years, respectively. Breast cancer was the most common tumor type (52% and 51%), followed by non-Hodgkin's lymphoma (21% and 18%) and lung cancer (11% and 15%). Hospitalization for neutropenic complications (narrow criterion) occurred during 2.1% of filgrastim cycles and 1.2% of pegfilgrastim cycles; hospitalization for neutropenic complications (broad criterion) occurred in a respective 4.8% and 3.1% of cycles; and hospitalization for all causes occurred in 8.7% and 6.3% of cycles (all, P < 0.01). The risks of hospitalization were consistently lower for chemotherapy cycles that involved pegfilgrastim prophylaxis compared with filgrastim prophylaxis (odds ratios = 0.64-0.73; P < 0.05).
CONCLUSION: The risk of hospitalization for neutro-penic complications during cancer chemotherapy in clinical practice was approximately one third higher among patients who received filgrastim prophylaxis than among those who received pegfilgrastim prophylaxis.