UGT1A1 and Decreased total neutrophil count: UGT1A1*28 heterozygotes (OR = 2.263, 95%CI 1.395–3.670), UGT1A1*28 homozygotes (OR = 5.910, 95%CI 1.138–30.682) and UGT1A1*6 homozygotes (OR = 4.737, 95%CI 1.946–11.533) were the independent predictive factors of severe neutropenia.