This risk was emphasized by a warning that was added to irinotecan labels in 2005 subsequent to a US Food and Drug Administration (FDA) recommendation, and it has been proposed that cancer patients may be genotyped for UGT1A1 prior to initiation of irinotecan therapy to enable a preemptive dose reduction for individuals with the UGT1A1*28 allele [13]. Here, UGT1A1 is linked to cancer.