[Influence of Next-Day Administration of Pegfilgrastim after FEC100 Chemotherapy in Japanese with Breast Cancer on Neutrophil Count].

Febrile neutropenia(FN)is one of the serious treatment-related toxicities after FEC100(5-fluorouracil 500mg/m2, epiru- bicin 100mg/m2, cyclophosphamide 500 mg/m2)chemotherapy for breast cancer. Granulocyte-colony stimulating factor(GCSF) is used as a support therapy for FN. Thus, we evaluated retrospectively the safety of administering pegfilgrastim the day after FEC100 chemotherapy in Japanese patients with breast cancer as compared with lenograstim. Grade 3 or 4 neutropenia was observed in 91.7% patients after pegfilgrastim administration and in 63.2% after lenograstim. The incidence rate of FN was 7.0%after pegfilgrastim administration and 9.7%after lenograstim, a difference that was not significantly different(p= 0.741). The mean relative dose intensity was good at 0.98 for pegfilgrastim and 0.97 for lenograstim. In conclusion, pegfilgrastim is not inferior to lenograstim in the incidence of FN. However, we do not recommend administering pegfilgrastim on the day after FEC100 therapy because it causes more severe neutropenia and has a high risk of FN. The timing of administration of pegfilgrastim in FEC100 therapy requires further study.