Factors Affecting the Upper Limit of the Methotrexate (MTX) CSF Levels Achievable in Children With Brain Tumors Treated With High-dose Intravenous MTX.

Little has been published in the medical literature on serum and cerebrospinal fluid (CSF) methotrexate (MTX) levels in children with brain tumors.Matched 24-hour serum and CSF MTX levels were studied after 113 treatments in 35 brain tumors patients.A correlation between the 24-hour serum levels of MTX and MTX dosage was observed after 113 treatments in all 35 patients (r=0.39, P 5 g/m MTX in previously irradiated children and after infusion of ≥10 g/m in nonirradiated children this difference did not reach statistical significance. CSF MTX levels plateau at doses of MTX 15 g/m putting in doubt the value of administering even higher doses of MTX.The 24-hour MTX CSF levels are higher in patients with active CSF disease. Doses of 15 g/m MTX as CSF levels plateau at this dose.