Methotrexate-associated alterations of the folate and methyl-transfer pathway in the CSF of all patients with and without symptoms of neurotoxicity

Abstract

Background. Severe neurotoxicity has been observed after systemic high-dose and intrathecal methotrexate (MTX) treatment. The role of biochemical MTX-induced alterations of the folate and methyl-transfer pathway in the development of neurotoxic symptoms is not yet fully elucidated. Procedure. MTX, 5-methyltetrahydrofolate, calcium folinate, S-adenosylmethionine, and S-adenosylhomocysteine were measured in the cerebrospinal fluid (CSF) of 29 patients with acute lymphoblastic leukemia (ALL) who were treated with high-dose MTX (5 g/m2) followed by calcium folinate rescue (3 × 15 mg/m2) and/or intrathecal (8-12 mg) MTX. Two patients developed subacute MTX-associated neurotoxicity. CSF was obtained by lumbal puncture 1-3 weeks after administration of MTX and shortly after the occurrence of neurotoxicity. The analytes were measured using HPLC assays with UV and/or fluorescence detection. Results. In non-toxic patients, CSF concentrations of 5-methyltetrahydrofolate and S-adenosylmethionine were in the normal range 2 weeks after administration of high-dose and intrathecal MTX followed by rescue. In contrast, when these patients received intrathecal MTX without rescue, 5-methyltetrahydrofolate concentrations were significantly decreased 12 days after the first MTX administration. S-adenosylmethionine concentrations were significantly decreased up to 45 days. The two patients suffering from neurotoxicity had decreased levels of 5-methyltetrahydrofolate and S-adenosylmethionine during or following toxicity. S-adenosylhomocysteine was determined in all samples of neurotoxic patients but was below the limit of quantification in most samples of nontoxic patients. Calcium folinate was not detected; MTX was present only in samples obtained during its infusion. Conclusion. Intrathecal MTX without folinate rescue as well as MTX-associated neurotoxicity are likely to be associated with specific alterations of the folate and methyl-transfer pathway. © 2008 Wiley-Liss, Inc.