UGT1A1 and neutropenia: Indeed, the results reported by Chen and colleagues (for Irinotecan 180 mg/m2) showed that grades 3–4 neutropenia occurred for 15% of the patients with wild-type UGT1A1 (1*/1*) and 30.8% of the patient with heterozygous UGT1A1 genotype (1*/28*) [17].