A multivariate logistic regression analysis was performed to analyze the influence of CYP3A4*1B, CYP3A4*18, CYP3A5*3, DPYD*2A, DPYD*5, DPYD c.1774C > T, UGT1A1*28, UGT1A1*6, ABCB1 c.1236C > T, ABCB1 c.3435C > T, ABCC2 c.3972C > T, and ABCG2 c.421C > A on neutropenia (all grades and severe neutropenia) at first and second cycles. The gene discussed is CYP3A5; the disease is neutropenia.