UGT1A1 and neutropenia: Among the 6 patients with wild-type UGT1A1*28, 1 and 4 patients experienced grade 4 leukopenia and neutropenia, and another patient experienced grade 4 thrombocytopenia, while among the 4 patients with heterozygous UGT1A1*28, 1 patient experienced grade 4 neutropenia.