In this study, we clearly demonstrated that the risk of ATD-induced leukopenia and G-CSF administration was biphasic; its incidence in the acute onset group was 37.2 per 1000 person-years (0.7% during the first 72 days) and that in the late onset group was 3.1 per 1000 person-years, which was 10 times lower than that in acute onset group, with the risk persisting for at least for 6 years. This evidence concerns the gene CSF3 and Decreased total leukocyte count.