Stereotactic Radiosurgery for Brain Tumors in Pediatric Patients

Abstract

!3rain tumors represent the most common solid tumor in children. Fractionated radiation therapy has been an important treatment modality in the mUlti-disciplinary management of these tumors. Stereotactic radiosurgery is the precise delivery of a single fraction of radiation and has been an important treatment option for adult brain tumor patients. Although the use of stereotactic radiosurgery in pediatric brain tumors is much less frequent, it represents an important alternative for patients with recurrent, surgically inaccessible or radioresponsive tumors. This article will review the results and logistical issues of this modality in the management of pediatric brain tumors.Key words: Radiosurgery, pediatric brain tumors. IntroductionBrain tumors represent the most common solid tumor in children and account for approximately 20% of all childhood malignancies. Radiation therapy has been an important treatment modality in the multi-disciplinary management of these tumors.Stereotactic radiosurgery (SRS) is a conformal radiation technique that has been used frequently in adult patients to treat a variety of intracranial tumors, functional disorders, and vascular malformations. Unlike conventional radiotherapy, SRS enables the neurosurgeon and radiation oncologist to deliver a high, single dose of radiation to a precisely defined radiographic target to stop tumor growth while minimizing the dose to the surrounding normal tissue. The technique has been criticized, though, over concerns' about single fraction treatment and the potential for normal tissue damage. Given these concerns, the use of stereotactic radiotherapy or fractionated SRS has been advocated for some tumors based on histology, size and location. This approach combines the radiobiologic advantages of fractionation with the precision of radiosurgery.Based on the extensive literature regarding the use of SRS in adult patients, this modality has been used for some pediatric brain tumors. The use of SRS for such tumors is particularly appealing for patients with recurrent, surgicaIly inaccessible, or radioresponsive tumors. This article will review the results of SRS in pediatric patients with brain tumors. MedulloblastomasMedulloblastomas account for 15% to 20% of all primary pediatric central nervous system (CNS) tumors and 40% of all posterior fossa pediatric tumors. Following maximal surgical resection, optimal management includes cran-

Gamma Knife Radiosurgery for Central Neurocytomas

“…Central neurocytomas usually arise from the neuronal cells of the septum pellucidum, fornix, or subependymal plate of the lateral or third ventricle, so these tumors are surrounded by cerebrospinal fluid and occur as a small tumor attached to normal structures. 7,8,10,16,26,27,31) Therefore, radiosurgery has a lower risk of radiation injury than conventional radiotherapy because of the small target volume, relatively low marginal dose for tumor growth control, and steep fall-off into the peripheral normal tissue. The present series included no complication caused by radiation-induced peripheral edema or radiation necrosis, and previous studies identified only one case of side effects (Table 2).…”

“…2,3,[5][6][7][8][9][10][11][12][13][14]16,19,31,32,36) They are usually located in the lateral ventricles with or without extension to the third ventricles in young adults. 2,3,8,10,19) Standard initial treatment for central neurocytomas is a total resection whenever possible.…”

“…3,4,6,7,11,12,14,15,17,21,24,27,29,30,32) Central neurocytoma tends to be radiosensitive, so postoperative conventional radiotherapy and radiosurgery have been used to treat residual tumors after incomplete surgical resection or recurrence. 15,20,[23][24][25][26]31,32,34) Gamma knife radiosurgery (GKS) is effective against postoperative residual tumors or local recurrences of central neurocytomas. [1][2][3]6,9,13,14,25,27,28,35,37) However, central neurocytoma is rare and often resected completely, with conservative treatment for the relatively small residual or recurrent tumors.…”

Gamma Knife Stereotactic Radiosurgery for Low-Grade Astrocytomas

“…The role of chemotherapy is not yet well defined [5,6] . In adults and children with unresectable or partially resected disease, radiotherapy can be used for treatment [6,8] . Chemotherapy is sometimes used in children in an effort to delay radiotherapy and the attendant neurocognitive side effects [14] .…”

“…Considerable controversy exists regarding the optimal therapy of patients with LGA [5][6][7] . There have been limited publications detailing the role of stereotactic radiosurgery in the treatment of patients with LGA [8,9] . This publication presents the Indiana University experience utilizing gamma knife stereotactic radiosurgery (GKSRS) in the treatment of LGA.…”