MTHFR and oral mucositis: In this analysis, we found that although MTHFR C677T/A1298C polymorphism did not significantly affect plasma MTX levels at 48 h, C677T was significantly correlated with oral mucositis (2.2 vs. 3.6 vs. 11.1%, P = 0.034, Table 5), leucopenia (38.5 vs. 50.3%, P=0.025, Table 5), and thrombocytopenia (22.0 vs. 32.4%, P = 0.028, Table 5) and that patients with C677T and T677T genotypes seemed to be more susceptible to those toxicities.