The results indicated that GSTP1 c.313A > G mutation (A/G + G/G vs. A/A genotype) (age-, menopause-, T-stage, N-stage, clinical stage-, molecular subtype-, and chemotherapy regimen/dose-adjusted OR 4.273, 95% CI 1.141–16.000, P = 0.031) was an independent variable associated with neutropenia. This evidence concerns the gene GSTP1 and Decreased total neutrophil count.