Intratumoral methotrexate kinetics in a patient with intracranial anaplastic ependymoma

Little is known about intratumoral anticancer drug concentration in childhood brain tumors. We were able to measure methotrexate (MTX) tumor concentrations directly in a cystic anaplastic ependymoma. Cyst fluid was obtained by puncture of a subgaleal Rickham reservoir connected to a catheter in the tumor cyst. MTX concentrations were determined by fluorescence polarization immunoassay and compared to serum concentrations. Maximum MTX concentrations in tumor and CSF were found at the end of MTX infusion. Twenty-four hour after MTX infusion the mean tumor concentration was significantly higher than in the serum indicating MTX retention and accumulation in the tumor cyst. An AUC(tumor)/AUC(serum) ratio of 1.95 was obtained. In response to the applied multiagent chemotherapy the clinical condition of our patient improved and the tumor showed partial response on MRI. Cystic ependymomas might benefit from high dose MTX especially because of drug retention in the tumor cyst.