Satoh et al. reported that irinotecan could be used more safely in patients of the wild-type or heterozygous group for UGT1A1*28 and *6 polymorphisms because the AUC0-24h of SN-38 was lower and thus the incidences of grade 3 or higher neutropenia and leukopenia were lower in those patients compared with the homozygous group [15]. This evidence concerns the gene UGT1A1 and Decreased total neutrophil count.