Although there were no significant differences between grade 3–4 neutropenia and patients with UGT1A1*28, the incidence of severe neutropenia in patients with hetero- and homozygous *28 was higher than patients with homozygous wild type, (OR 2.7, 95% CI 0.8–8.8; P = 0.087). The gene discussed is UGT1A1; the disease is neutropenia.