Based on observations from previous clinical trials, a meta-analysis of 9 studies (81 patients with lymphoma and 740 with advanced colorectal cancer) evaluated the clinical correlation between severe post-irinotecan toxicities as grade 3-4 diarrhea and neutropenia, and occurrence of UGT1A1*1/UGT1A1*28 genotypes in both homozygous and heterozygous carriers. The gene discussed is UGT1A1; the disease is colorectal cancer.