Introduction
Medulloblastoma (MB) is one of the most common malignant brain tumors in children[1]. Approximately one-third of children present with a high risk of disease at the time of diagnosis. The survival of these patients remains unfavorable, and the 5-year progression-free survival (PFS) rate is >60% in the last few years by different strategies[2]. Most recently, a clinical trial shows that for children aged over 5 years with high-risk MB, the 5-year PFS is 76% after high-dose chemotherapy with stem cell support followed by conventional craniospinal radiation therapy and maintenance treatment [3]. The survival rate obtained in this trial is in the upper range of the recently obtained encouraging results from different studies[2, 4]. In contrast to standard-risk MB, there is no gold standard treatment for high-risk MB. Even though, it seems that treatment based on high-dose chemotherapy and conventional radiotherapy can result in a high survival rate in children with newly diagnosed high-risk MB.
In our institution, autologous stem-cell transplantation is not routinely performed due to its high cost. In addition, it also brings a burden on 6-14% of patients who are associated with death[5]. In view of this, methotrexate (MTX) intrathecal injections were adopted for high risk MB. Due to the relative lack of data concerning the efficacy and toxicity of MTX intrathecal injections in central nervous system (CNS) embryonal tumors, it remains controversial about whether MTX intracranial injection should be administered. MTX has been used in European trials, but it is rarely adopted in the United States because of the association with radiation-induced leukoencephalopathy. To the best of our knowledge, there is no previous study reporting acute leukoencephalopathy induced by MTX treatment for MB during chemotherapy.
Here, a retrospective study was conducted to evaluate the therapeutic benefits of intrathecal MTX in children aged over three years with high-risk MB, so as to objectively evaluate the intervention and side effects, especially leukoencephalopathy for children with high risk MB.