Safety and Efficacy of Pegfilgrastim When Given Less Than 14 Days Before the Next Chemotherapy Cycle: Review of Every 14-Day Chemotherapy Regimen Containing 5-FU Continuous Infusion

Background:Pegfilgrastim should not be given <14 days from the next chemotherapy because of concerns for cytopenias. Some clinicians are prescribing pegfilgrastim to be given <14 days in patients receiving 5-fluorouracil continuous infusion (5-FUCI) regimens. Objective: To determine the effectiveness and safety of pegfilgrastim administered <14 days from the next chemotherapy in patients receiving 5-FUCI administered >46 hours. Methods: Single-institution retrospective cohort study of patients who received 5-FUCI administered >46 hours from June 2013 to December 2015. The unit of measurement was chemotherapy cycles. End points included the safety and efficacy of giving pegfilgrastim <14 days from the next chemotherapy (Pegfilgrastim-Less-Than-14-Days-Group) and comparing that to pegfilgrastim given ≥14 days (Pegfilgrastim-More-Than-14-Days-Group), filgrastim only (Filgrastim-Group), and no colony stimulating factors (No-CSF-Group). Generalized estimating equations (GEEs) were used to compare mean absolute neutrophil count (ANC) and white blood cell count (WBC). Poisson regression models with GEE were used to estimate relative risk (RR) for neutropenia. Results: There were no incidences of neutropenia, febrile neutropenia (FN), or hospitalizations for FN with the Pegfilgrastim-Less-Than-14-Days-Group. There was also a high mean ANC of 9.9 (5.7) × 10⁹/L. Mean ANC and WBC were statistically significantly less with the Filgrastim-Group, No-CSF-Group, and Pegfilgrastim-More-Than-14-Days-Group compared with the Pegfilgrastim-Less-Than-14-Days-Group. The Filgrastim-Group and the No-CSF-Group had a 32% (1.10-1.56, P = 0.002) and 8% (1.04-1.12, P < 0.001) increased risk of incidence of neutropenia, respectively, compared with the Pegfilgrastim-Less-Than-14-Days-Group. The risk of incidence of neutropenia was the same with the Pegfilgrastim-More-Than-14-Days-Group and Pegfilgrastim-Less-Than-14-Days-Group (0.95-1.04, P = 0.821). Conclusion: This study shows a promising possibility that administering pegfilgrastim <14 days from the next chemotherapy cycle could be a safe and effective practice. However, better controlled clinical trials are needed.