Diffuse astrocytomas may be less amenable to total resection, and this may account for the poorer outcome. The extent of resection necessary for cure, as noted above, is unknown because patients with microscopic and even gross residual tumor after surgery may experience long-term PFS without postoperative therapy.[2,9,14] The long-term functional outcome of cerebellar pilocytic astrocytomas is relatively favorable. Full-scale mean IQs of patients with low-grade gliomas treated with surgery alone are close to the normative population. However, long-term medical, psychological, and educational deficits may be present in these patients.[18,19][Level of evidence: 3iiiC]
Low-grade astrocytomas that occur in midline structures (e.g., hypothalamus, thalamus, brain stem, and spinal cord) can also be aggressively resected, with resultant long-term disease control;[11,12,20]; [Level of evidence: 3iiiA] however, such resection may result in significant neurologic sequelae, especially in children younger than 2 years at diagnosis.; [Level of evidence: 3iC] Because of the infiltrative nature of some deep-seated lesions, extensive surgical resection may not be appropriate and biopsy only should be considered.[Level of evidence: 3iiiDiii] Treatment options for patients with incompletely resected tumor must be individualized and may include observation, a second resection, chemotherapy, and/or radiation. A shunt or other cerebrospinal fluid diversion procedure may be needed.
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. Approximately 50% of patients with less-than-gross total resection may have disease that remains progression-free at 5 to 8 years, supporting the observation strategy in selected patients.
Radiation therapy is usually reserved until progressive disease is documented,[16,26] and its use may be further delayed through the use of chemotherapy, a strategy that is commonly employed in young children.[27,28] 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.[11,17,29,30]; [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 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.