Following resection, immediate (within 48 hours of resection per Children's Oncology Group [COG] criteria) postoperative magnetic resonance imaging is obtained. Surveillance scans are then obtained periodically for completely resected tumors, although the value following the initial 3- to 6-month postoperative period is uncertain.; [Level of evidence: 3iiDiii] In selected patients in whom a portion of the tumor has been resected, the patient may also be observed without further disease-directed treatment, particularly if the pace of tumor regrowth is anticipated to be very slow.
Radiation therapy is usually reserved until progressive disease is documented,[14,24] and its use may be further delayed through the use of chemotherapy, a strategy that is commonly employed in young children.[25,26] Radiation therapy results in long-term disease control for most children with chiasmatic and posterior pathway chiasmatic gliomas, but may also result in substantial intellectual and endocrinologic sequelae, cerebrovascular damage, and possibly an increased risk of secondary tumors.[10,15,27,28]; [Level of evidence: 2C] An alternative to immediate radiation therapy is subtotal surgical resection, but it is unclear how many patients will have stable disease and for how long. Radiation therapy and alkylating agents are used as a last resort for patients with neurofibromatosis type 1 (NF1), given the theoretically heightened risk of inducing neurologic toxic effects and second malignancy in this population. Children with NF1 may be at higher risk for radiation-associated secondary tumors and morbidity due to vascular changes.
For those children with low-grade glioma for whom radiation therapy is indicated, conformal radiation therapy or stereotactic radiosurgery approaches appear effective and offer the potential for reducing the acute and long-term toxicities associated with this modality.[31,32]; [Level of evidence: 2A]; [Level of evidence: 2C]; [Level of evidence: 3iiiDi]; [21,35][Level of evidence: 3iiiDiii]
Given the side effects associated with radiation therapy, chemotherapy may be particularly appropriate for patients with NF1 and for younger children.
Chemotherapy may result in objective tumor shrinkage and will delay the need for radiation therapy in most patients.[25,26,36,37] Chemotherapy has been shown to shrink tumors in children with hypothalamic gliomas and the diencephalic syndrome, resulting in weight gain in those who respond to treatment.
The most widely used regimens to treat progression or symptomatic nonresectable, low-grade gliomas are carboplatin with or without vincristine[25,26,39] or a combination of thioguanine, procarbazine, lomustine, and vincristine. Other chemotherapy approaches have been employed to treat children with progressive low-grade astrocytomas, including multiagent platinum-based regimens [26,36,40]; [Level of evidence: 2Diii] and temozolomide.[42,43]
Reported 5-year progression-free survival rates have ranged from approximately 35% to 60% for children receiving platinum-based chemotherapy for optic pathway gliomas,[26,36] but most patients ultimately require further treatment.