Pediatric glial tumors

Abstract

Glial neoplasms in children comprise many heterogeneous tumors that include pilocytic and fibrillary astrocytomas, ependymomas, and the diffuse intrinsic pontine gliomas. In contrast to adults, most of whom present with high-grade fibrillary neoplasms, alternate histologies represent most cases seen in the pediatric setting. In addition, although most adult gliomas are supratentorial in location, in pediatrics infratentorial tumors (posterior fossa and brain stem) predominate. We discuss three specific tumors: diffuse intrinsic pontine gliomas; pilocytic astrocytomas; and ependymomas. Maximal surgical resection is the mainstay of therapy for both pilocytic astrocytomas and ependymomas. Failure to achieve an optimal resection often results in progression and the need for further therapy for patients with pilocytic astrocytomas, and is ultimately fatal in most children with subtotally resected ependymomas. Surgical resection has no role in the treatment of pontine gliomas. Focal radiation therapy is included routinely in the treatment of ependymomas, and it has been shown to improve event-free survival. This therapy also is used in the treatment of pontine gliomas because radiation treatment appears to slow inevitable tumor progression. Radiation therapy in pilocytic astrocytomas is generally reserved for patients who progress after an initial surgical resection or for those patients with midline tumors; these patients are poor candidates for aggressive surgical resection. The role of chemotherapy in these tumors is in evolution. Chemotherapy for pilocytic astrocytomas, particularly in young children (for whom radiation therapy is avoided), appears to be effective in the treatment of a subset of patients. Up-front chemotherapy is generally reserved for the youngest children who present with ependymoma. In the recurrence setting, chemotherapy has shown some activity, although this approach is never curative. Despite the application of various chemotherapeutics and other biologic agents, none of these therapies has improved the prognosis for patients with the uniformly lethal pontine glioma.

Leksell Gamma Knife treatment for pilocytic astrocytomas: long-term results

“…The fractionation scheme was selected according to 1) the previous treatment modality (fractionated scheme for all patients pretreated by EBRT); 2) the location of the lesion (a fractionated scheme was used in tumors located in an eloquent region or in those which were in contact with the brainstem; in cases involving contact with the optic pathway 10 fractions were used over a period of 5 days, with the time interval between fractions being longer than 6 hours); and 3) larger volumes. Patients irradiated with a single fraction had the following characteristics: no previous EBRT, cerebellar location without contact with the brainstem or optic nerve, tumor volume not larger than 4800 mm 3 , and repeat resection not recommended by neurosurgeons ( Fig. 1).…”

“…Radical neurosurgical resection provides the best therapeutic results and remains the main therapy option for low-grade gliomas. 3,8,10,13,18,25,29 However, the optimal treatment strategy for pilocytic astrocytomas following subtotal neurosurgical resection or for unresectable tumors has not been strictly defined and remains controversial. The consensus seems to favor observation and delaying radiotherapy until recurrence or progression is detected clinically or by imaging.…”

“…Although they represent between 1% and 5% of all intracranial tumors and 1.7%-7% of glial tumors, pilocytic astrocytomas are common brain tumors in children (representing 70%-80% of cerebellar astrocytomas). 3,8,27 Most are located in the cerebellar hemispheres, in the vermis, in the third and fourth ventricles, in the hypothalamus, and in the parasellar region. Radical neurosurgical resection provides the best therapeutic results and remains the main therapy option for low-grade gliomas.…”

“…[9][10][11][12][13][14][15][16][17]28 Pilocytic astrocytomas tend to proliferate very slowly, and the evaluation of treatment results requires prolonged follow-up (at least 10 years) after total resection. 3,8,13,18,25,29 Malignant transformation of pilocytic astrocytomas and meningeal infiltration has only rarely been described.…”

Primary Pilocytic Astrocytoma with Malign Transformation

“…The treatment is surgical excision and chemotherapy (CT) and radiotherapy (RT) treatment can be applied in the presence of residual tumor or recurrence [2,3]. After total resection, the 10 year and 20 year surveys are 95.8% and 82%, respectively.…”