INTRODUCTION: Pegfilgrastim is a PEGylated formulation of filgrastim with a long half-life. It is highly convenient and less burdensome for patients. However, white blood cell count may temporarily increase after administration; in particular, a leukocyte overshoot may be observed. The present study retrospectively examined the incidence and timing of leukocyte overshoot after pegfilgrastim administration. PATIENTS AND METHODS: Fifty-five patients (118 occasions of pegfilgrastim) were evaluated. Leukocyte overshoot was defined as white blood cell count ≥10,000/mm3 exceeding the reference value. RESULTS: Leukocyte overshoot was observed in 71.2% (84/118) occasions, in 76.4% (42/55) patients. The maximum white blood cell count ≥30,000/mm3 was observed in 30.5% (36/118) occasions in 45.5% (25/55) patients and was observed in 39.3% (33/84) occasions on day 1 after pegfilgrastim administration and 26.2% (22/84) on day 2. Leukocyte overshoot has been observed in only 23.1% (9/39) patients administered with normal granulocyte colony-stimulating factor. However, there were no patients with white blood cell counts ≥30,000/mm3. CONCLUSION: There was a higher frequency of occurrence of leukocyte overshoot in response to pegfilgrastim than in response to normal granulocyte colony-stimulating factor. High incidence of leukocyte overshoot was observed when blood was collected 1-2 days after administration of pegfilgrastim. It is important for patients to understand the characteristics of pegfilgrastim by conducting pharmaceutical guidance.
INTRODUCTION: Pegfilgrastim is a PEGylated formulation of filgrastim with a long half-life. It is highly convenient and less burdensome for patients. However, white blood cell count may temporarily increase after administration; in particular, a leukocyte overshoot may be observed. The present study retrospectively examined the incidence and timing of leukocyte overshoot after pegfilgrastim administration. PATIENTS AND METHODS: Fifty-five patients (118 occasions of pegfilgrastim) were evaluated. Leukocyte overshoot was defined as white blood cell count ≥10,000/mm3 exceeding the reference value. RESULTS: Leukocyte overshoot was observed in 71.2% (84/118) occasions, in 76.4% (42/55) patients. The maximum white blood cell count ≥30,000/mm3 was observed in 30.5% (36/118) occasions in 45.5% (25/55) patients and was observed in 39.3% (33/84) occasions on day 1 after pegfilgrastim administration and 26.2% (22/84) on day 2. Leukocyte overshoot has been observed in only 23.1% (9/39) patients administered with normal granulocyte colony-stimulating factor. However, there were no patients with white blood cell counts ≥30,000/mm3. CONCLUSION: There was a higher frequency of occurrence of leukocyte overshoot in response to pegfilgrastim than in response to normal granulocyte colony-stimulating factor. High incidence of leukocyte overshoot was observed when blood was collected 1-2 days after administration of pegfilgrastim. It is important for patients to understand the characteristics of pegfilgrastim by conducting pharmaceutical guidance.