Introduction

The presentation and management of primary brain tumors has been one of the more frustrating experiences in oncology. While good outcomes are certainly possible, the intricacy of the affected organ and the poor tolerance of therapy often spell significant debilitation for patients, dramatically affecting quality of life. Unlike most cancers in the body where metastatic disease most frequently leads to patient death, primary brain tumors rarely metastasize. Still, malignant brain tumors are rarely cured due to limitations of effectiveness and tolerance of local therapies. Even benign tumors in the brain constitute a profound threat to both a patient's quality of life and survival. As such, management strategies for primary brain tumors must be equally sensitive to quality of life issues as survival since the therapy ultimately will often fail the patient for controlling the tumor.

Natural history

There are four types of glial cells that give rise to a variety of brain tumors: astrocytes, oligodendrocytes, ependyma, and microglia. Tumors arising from astrocytes are called astrocytomas including pilocytic astrocytoma (grade I), fibrillary astrocytoma (grade II), anaplastic astrocytoma (grade III) and glioblastoma multiforme (GBM, grade IV). Oligodendrocytes give rise to oligodendrogliomas, which are usually low grade but can be anaplastic. Ependymomas occur in and around the ventricles, commonly in the fourth ventricle of the posterior fossa. Although ependymomas are only occasionally malignant, they are often infiltrative at the primary site and may disseminate through the cerebrospinal fluid (CSF).