We found that polymorphism of rs1537514 showed the most significant effect: heterozygote associated with better clinical benefit (P = 0.002) and decreased risk of grade 3 or 4 gastrointestinal toxicity (P = 0.027), while the mutant homozygote associated with increased risk of severe gastrointestinal toxicity (P = 0.031) and thrombocytopenia (P = 009).