Brain stem gliomas compose 15-20% of all childhood CNS tumors. The median age at presentation is 6-7 years of age. Fifty percent of the patients present with cranial nerve and long tract signs.
The majority of patients have diffuse, infiltrating pontine tumors, sometimes with an exophytic component. These are typically WHO grade II-IV gliomas with a median survival of less than 1 year, and 2-year survival rates of <10-20%. A subset of patients have focal lesions that are usually grade I tumors who have 2-year survival rates of about 60% or greater. Localized brain stem tumors may also be PNETs. Although sensitivity to chemotherapy as well as radiation is common, prognosis remains poor, at around 10%.
Surgical resection is not usually possible because of the proximity to vital structures, limited room for expansion and swelling, and possible damage to medullary structures. There is no apparent benefit from a surgical biopsy when the imaging and clinical picture are indicative of a diffuse infiltrating pontine glioma. For focal tumors (nontectal), complete resection may be safe and may not require any further therapy. Partial resection of exophytic tumors will establish the diagnosis and reduce the obstructing mass within the fourth ventricle. If hydrocephalus is present, a CSF diversion should be performed.
Limited field irradiation is standard palliative care in patients with infiltrative pon-tine gliomas. A tumor dose of approximately 5400 cGy is standard. The treatment field should include the extent of the defined tumor and a 2-cm margin around the tumor. In irradiating these tumors, precaution should be taken to minimize brain stem edema, especially in patients who have not been shunted. The use of high-dose steroids is valuable during treatment and may be required throughout the treatment period. Children with diffusely infiltrating pontine gliomas often initially respond to radiation therapy but progressive disease is usually seen within 8-12 months. Timing of radiation for partially resected focal lesions is unclear. It is not known whether immediate adjuvant therapy is superior to observation and chemotherapy when progression occurs.
The use of combination chemotherapy after radiotherapy has not improved the disease-free survival in brain stem tumors. Until some chemotherapeutic regimen confirms a survival advantage in newly diagnosed patients, chemotherapy plays a palliative role.
The overall prognosis for brain stem tumors is poor. Most centers report a 5-20% 5-year survival rate when high doses of irradiation are employed. Children with diffusely infiltrating pontine gliomas often respond initially to radiation therapy but progressive disease is usually seen within 8-12 months. Improved survival is seen in focal low-grade brain stem astrocytomas especially those seen in patients with NF-1 and those in the tectal area.
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