PRIMARY INTRACRANIAL TUMORS
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Astrocytomas Including Glioblastomas
Infiltrative tumors with a presumptive glial cell of origin. Most common primary intracranial neoplasm. Only known risk factors are ionizing radiation, uncommon hereditary syndromes (neurofibromatosis, tuberous sclerosis), and immunosuppression (primary CNS lymphoma). Infiltration along white matter pathways often prevents total resection. Imaging studies (Fig. 75-1) fail to indicate full tumor extent. Grade I tumors (pilocytic astrocytomas) are the most common tumor of childhood, typically in the cerebellum; can be cured if completely resected. Grade II astrocytomas usually present with seizures in young adults; if feasible should be surgically resected. In pts at higher risk for recurrence (subtotal resection or above the age of 40 years), radiation therapy (RT) followed by PCV (procarbazine, (cyclohexylchloroethylnitrosourea [CCNU]), and vincristine) chemotherapy may possibly be of benefit. The tumor transforms to a malignant astrocytoma in most pts, leading to variable survival with a median of about 5−10 years. Grade III (anaplastic astrocytoma) and grade IV (glioblastoma) astrocytomas are treated similarly with maximal safe surgical resection followed by RT with concomitant temozolomide, followed by 6–12 months of adjuvant temozolomide. With this regimen, median survival is increased to 14.6−18 months compared to only 12 months with RT alone, and 5-year survival is approximately 10%. Despite optimal therapy, glioblastomas invariably recur. Treatment options for recurrent disease may include reoperation, carmustine wafers, and alternate chemotherapeutic regimens. Reirradiation is rarely helpful. Bevacizumab, a humanized vascular endothelial growth factor (VEGF) monoclonal antibody, increases progression-free survival but not overall survival.