This study assessed the effect of pegfilgrastim in patients with early stage breast cancer who were receiving docetaxel and cyclophosphamide(TC)therapy(75mg/m / 2 docetaxel plus 600 mg/m2 cyclophosphamide). In total, 17 patients who were to receive 4 planned cycles of TC therapy every 3 weeks were included in this study. Of the 17 patients, 10 who received pegfilgrastim after January 2016 formed the Peg-G group and 7 who did not receive pegfilgrastim until December 2015 formed the control group. We observed a high successful execution rate and relative dose intensity(RDI)with docetaxel in both groups. The successful execution rates were 100% in the Peg-G group and 42.8% in the control group. The RDI was 86.5%(65.4-100%)in the Peg-G group and 52.5%(48.0-58.0%)in the control group. This study showed that the use of pegfilgrastim results in a high successful execution rate and RDI in patients with early stage breast cancer undergoing TC therapy.