Central Nervous System / Brain Tumor
Tumors of the central nervous system (CNS) are seen in both pediatric and adult populations. These tumors can be non-cancerous (benign) or malignant (cancerous). There are approximately 4,130 cases yearly of malignant and benign brain tumors.
Brain tumors occur in both kinds of cells that make up the brain tissue. They are the nerve cells and the supporting (or glial) cells that protect and take care of the nerve cells. There are many more supporting cells than nerve cells, so cancers of the supporting cells are the most common. These are astrocytomas and gliomas.
Most have no associated cause. These rare tumors can have widely varying presentations. Weakness, numbness, and mental changes are some examples of localized brain dysfunction. Headaches may result from the mass effect of the cancer which can be associated with nausea, vomiting, fatigue, and vision problems. Tumors of the spinal canal can present with pain in the region of the tumor, numbness, weakness and bowel or bladder dysfunction. The diagnosis is typically made by computer tomography (CT) and magnetic resonance imaging (MRI), with MRI being the superior choice since it is much better for imaging the nervous system. Tumors can be divided by their location, cell of origin, histologic appearance, or the age group they affect. Tumors are arranged by their malignancy potential (i.e., aggressive) or grade.
Guidelines for treatment can include surgery, radiation, and chemotherapy, dependent upon the type and location of the tumor. The goal of surgery is relief of symptoms and/or tissue type diagnosis, and reduction of the size of the tumor. It is usually not curative for many tumors, but it may be able to cure lower grade tumors. One must consider the patient’s age, overall medical/neurologic condition, likely diagnosis, and possible complications to determine if the surgery could be done.
Radiation plays a significant role in the treatment of tumors that arise in the CNS, as well as those that spread there from other cancers (i.e., such as lung and breast cancer). The degree of success depends on the responsiveness of the tumor to doses that the CNS can tolerate. The radiation is typically given five days a week in fractionated technique at 180 to 200 cGy per day to a dose of 5,400 to 6,000 cGy, given over 6 to 6 ½ weeks. At this dose, 5% of the patients would be expected to develop symptoms of radiation injury within five years. These doses can provide durable control for less aggressive, lower grade tumors. However, the most aggressive tumor, glioblastoma multiforme (GBM/Grade IV tumor) is less responsive to radiation at these doses. There has been some improvement with the addition of Temador (temozolomide) during radiation for GBM. An effective dose of radiation has not been found so the dose is limited to the tolerance of CNS. The use of specialized techniques has allowed us to increase the dose in certain situations. IMRT (intensity modulated radiation therapy) and stereotactic radiotheraphy (one treatment fraction)/radiotherapy (2 to 5 fractions) have the advantage of distributing radiation doses more precisely within a radiographically defined area while maximally sparing normal brain tissue. These techniques are finding their way into treating primary tumors, as well as patients with recurrent CNS tumors. Whole brain radiation treatments are most commonly used for treatment of multiple brain metastases where more focal treatment would be inadequate. The dose is typically 3,000 to 3,750 cGy given in 10 to 15 fractions, over 2 to 2 ½ weeks. More focal partial brain radiation is typically used for most other situations to spare the most normal brain tissue from possible radiation side effects.
Chemotherapy has a much more limited role in CNS tumors. Primary central nervous system lymphoma (PCNSL) is an unusual, more aggressive form of non-Hodgkin’s lymphoma where chemotherapy has taken a greater role.