Most of the previous studies retrospectively evaluated relatively small numbers of patients with different types of cancer who received various irinotecan-based regimens, although the UGT1A1*28/*28 genotype was associated with a two-fold higher risk of diarrhoea than wild-type genotype in a meta-analysis limited to Caucasians with colorectal cancer (Liu et al, 2014). Here, UGT1A1 is linked to colorectal cancer.