According to manufacturers' recommendations (Amgen: Neupogenᵀᴹ), filgrastim are to start 24 hrs after the last dose of chemotherapy and continue until absolute neutrophil count (ANC) has recovered to within the normal range (or for 14 days). However, for economic and practical reasons and/or patient's convenience, it has been common practice to initiate filgrastim at a later days of cycle and/or administer a shorter course of treatment. Data from several clinical studies have shown that 10-11 days' filgrastim treatment is required for optimal prophylaxis for febrile neutropenia (FN), and data from other cancers shows that suboptimal use of G-CSFs could deteriorate clinical outcomes. However, in two recent randomized study with breast cancer patients undergoing TAC chemotherapy, acceptable incidence (7-18%) of FN was shown with the consecutive 6 or 7-daily filgrastim schemes. Also, although there is theoretical concern that there can be wide fluctuations in the patient's ANC over time in alternate or intermittent filgrastim administration, because there was no difference in clinical outcomes between daily- or intermittent-dose filgrastim schedules in previous literatures, the intermittent every other day of 5 shot-filgrastim scheme would have clinical outcomes comparable with previous consecutive 6 or 7-daily filgrastim schemes in coverage of ANC nadir. Therefore, it can be justified to investigate the non-inferiority of intermittent every other days of 5 shot-filgrastim scheme compared with control arm using of pegfilgrastim on D2.