Incidence of toxicity based on specific genotypes. Cumulative incidence of the first episode of grade 3 to 4 gastrointestinal (GI) toxicity differing (P = .014) by RFC genotypes during therapy (top). Cumulative incidence of the first episode of grade 3 to 4 hyperbilirubinemia differing (P < .001) by UGT1A1 genotypes, during therapy (bottom).