As per heterochronic follow-up, which has not been reported previously, day four injection of PEG-G-CSF appears more effective than day three injection for preventing neutropenia. However, due to the small number of cases in this series and the confounding factor of the chemotherapy dose in the third cycle being approximately 8% less than that in the first cycle in Case 2, it is difficult to generalize our findings. Here, CSF3 is linked to Decreased total neutrophil count.