Influence of plasma methotrexate level and MTHFR genotype in Korean paediatric patients with acute lymphoblastic leukaemia.

Whether plasma MTX concentrations and MTHFR C677T and A1298C polymorphisms could be used as a predictor of occurrence of MTX-related toxicities in Korean paediatric patients with acute lymphoblastic leukaemia (ALL) were assessed. HD-MTX related toxicities, MTHFR polymorphisms and MTX plasma concentrations following 337 HD-MTX cycles to 117 children with ALL on maintenance therapy were analyzed. A significantly higher frequency of hyperbilirubinemia (P = 0.0443) and renal toxicity (P = 0.0107) were associated with high MTX concentrations by Fisher's exact test. Moreover, high MTX concentrations at 24 h, 48, and 72 h were significantly associated with increased frequency of vomiting (P < 0.05) and hyperbilirubinemia (P < 0.05) by Mann-Whitney U test. There was a significantly higher frequency of mucositis in patients with the MTHFR 677 TT genotype (P = 0.0273) and a significantly higher frequency of MTX dose reduction in patients with the 677 TT genotype (P = 0.0217), compared to the CC/CT genotype. Independently, plasma MTX concentrations and MTHFR C677T genotype could be useful markers for tailoring MTX dosing and monitoring adverse effects in childhood ALL HD-MTX therapy in Korean patients.