• CYP2B6 -750T>C → GI toxicity (OR = 0.238; 95% CI = 0.107–0.523; p < 0.001); Leukocytopenia (OR = 0.347; 95% CI = 0.173–0.699; p < 0.001)• CYP2C19*2 c.681G>A → GI toxicity (OR = 0.157; 95% CI = 0.057–0.430; p < 0.001); Leukocytopenia (OR = 0.194; 95% CI = 0.092–0.409; p < 0.001); Infection (OR = 0.260; 95% CI = 0.119–0.568; p < 0.001)• GSTP1 c.313A>G → OR = 1.791; 95% CI = 0.835–3.839; p > 0.05); Leukocytopenia (OR = 1.821; 95% CI = 0.953–3.482; p > 0.05). Here, GSTP1 is linked to infection.