Timing of Pegfilgrastim: Association with Febrile Neutropenia in a Pediatric Solid and CNS Tumor Population.

Background: While recommended timing of pegfilgrastim administration is ≥24 h after chemotherapy, patient barriers to next day administration, available adult evidence, and pharmacokinetic data have led to earlier administration in some pediatric patients with solid and central nervous system tumors. The purpose of this study was to compare patient outcomes by timing of pegfilgrastim after chemotherapy. Methods: A retrospective chart review examined timing of 932 pegfilgrastim administrations to 182 patients, 0-29 years of age. The primary outcome was febrile neutropenia (FN); the secondary outcome was neutropenic delays (ND) ≥7 days to next chemotherapy cycle. To account for multiple pegfilgrastim administrations per patient, a generalized mixed model was used with a logit link for the dichotomous outcomes (FN & ND), timing as the dichotomous independent variable, and random effect for patient. Results: FN occurred in 196 of 916 cycles (21.4%); and ND in 19 of 805 cycles (2.4%). The fixed effect of pegfilgrastim administration < or ≥24 h after chemotherapy was not significant, p = .50; however, earlier or later than 20 h was significant, p = .005. FN odds were significantly higher when pegfilgrastim was given <20 h (OR 1.78, 95% CI: 1.19-2.65) after chemotherapy, which may be attributable to differences in chemotherapy toxicity regardless of pegfilgrastim timing. Discussion: While attempts should be made to administer pegfilgrastim ≥24 h after chemotherapy, if barriers exist, modified timing based on individual patient characteristics should be considered. Prospective randomized trials are needed to identify lower risk patients for early pegfilgrastim administration.