Brain Cancer
Gliomas are a class of tumor that develops from glial (neuroepithelial or support) cells, which compose the supportive tissue of the brain. Cells called astrocytes, ependymal and oligodendroglia are all examples of glial cells. Gliomas comprise nearly one-half of primary brain tumors and one-fifth of all primary spinal cord tumors. Low-grade gliomas are slow growing and are assigned either a I or II grade. The grade of a tumor depends on how abnormal the cancer cells look under a microscope and how quickly the tumor is likely to grow and spread. Grade I tumors resemble normal cells and tend to grow and multiply slowly. Grade I tumors are generally considered the least aggressive in behavior. Conversely, the cells of Grade III or Grade IV tumors do not look like normal cells of the same type.
High-grade (malignant) gliomas grow much more quickly and are assigned either a III (anaplastic) or IV (glioblastoma multiforme) grade. Combined, grade III and IV gliomas represent about 40 percent of all primary brain tumors in patients 40-49 years of age, and 60 percent in patients over 60. In most clinical series, grade III tumors comprise approximately 10 percent and grade IV 90 percent of the total number of high-grade, malignant primary brain tumors.
Malignant gliomas are one of the most devastating tumors that can affect any individual. Nevertheless, this past decade, major advances in the fields of molecular biology and cellular biology, as well as genomics, have begun to improve our understanding of malignant gliomas. Grade IV gliomas, often referred to as glioblastoma multiforme or GBM, possess multiple genetic and chromosomal abnormalities that cause these tumors to grow rapidly. These tumors are unique in their ability to multiply uncontrollably, and aggressively invade, infiltrate and destroy neighboring areas of the brain. However, it is very rare for such tumors to metastasize (spread) outside the central nervous system. As a GBM progresses, portions of the tumor often outgrow the immediate blood supply and die. In contrast, outer regions of the tumor readily supply the growth of new blood vessels (angiogenesis), enabling continued rapid growth of the GBM.
Symptoms
The presenting symptom(s) of a glioma depend on the location of the tumor within the brain and its rate of growth. Common symptoms include headaches, seizures, difficulty speaking, weakness/paralysis in one part of the body or face, difficulty with vision, impairment of sensation, impairment of balance, nausea/vomiting, behavioral changes, and impairment of memory or thinking. The clinical course of an untreated malignant glioma is characterized by relentless invasive growth and, even with treatment, near-universal recurrence.
Diagnosis
Most patients harboring a malignant glioma have had one or more of the above-mentioned symptoms for several weeks or months. Occasionally, a patient may present with no prior neurological symptoms. In this uncommon scenario, the glioma is discovered "incidentally" on a head CT scan performed on a patient for other reasons, such as an auto accident or a fall with associated head trauma.
In evaluating most brain tumors, MRI of the brain is usually preferred over a CT scan. MRI is better at establishing a probable diagnosis and portraying the suspected brain tumor in three planes, thereby allowing more exact localization of the tumor in relation to critical areas of the brain. Multivoxel magnetic resonance spectroscopy is another way to evaluate gliomas. MRS is a new form of brain scan that uses state-of-the-art software to analyze radio waves to give a "chemical fingerprint" of a brain lesion noninvasively. Furthermore, positron emission tomography (PET) scanning can provide further information about the chemical functioning of a metabolic potential of a brain tumor. Although these noninvasive diagnostic tests are helpful, the most accurate way to diagnose a glioma is to examine tissue samples obtained from a biopsy of the tumor. Once a definitive diagnosis has been established, a customized treatment plan is developed for the individual patient, based on his or her unique circumstances.
Treatments
Traditional treatment options for malignant gliomas include surgery, radiation therapy and chemotherapy.
Surgery
Surgery is the primary treatment for malignant gliomas. A window is cut into the skull to access the tumor. The goal of surgery is to remove as much of the visible tumor as possible without damaging normal neurological functions. An array of new technologies, such as operating microscopes, microdissection techniques, computerized image-guidance, ultrasound performed during surgery, brain mapping, and most recently, real-time MR imaging, makes removal of gliomas safer than ever. Patients who can have 97 percent of the tumor removed appear to have a definite increase in survival, especially if the tumor is located in the frontal lobe of the brain.
Although surgery does not always cure the brain tumor, it can immediately alleviate symptoms caused by the tumor and improve the effectiveness of other therapies; if not removed, some parts of the tumor tend to be particularly resistant to radiation and chemotherapy. Removal of the glioma provides pathologists with important tissue samples that can better help analyze the tumor.
Radiation Therapy and Chemotherapy
Radiation therapy and chemotherapy are widely used as secondary treatments following surgery. Both therapies may help suppress the growth of the tumor. Among patients who are not surgical candidates, either radiation or chemotherapy can be used as an initial treatment, but typically only after a biopsy has established the diagnosis of malignant glioma.
Patients who are not candidates for surgery generally include those who
- are medically unstable
- have multiple active cancers simultaneously
- have tumors spread to both brain hemisphere
- have a glioma in an inoperable location (e.g., brain stem)
- are opposed to surgery
Complications of Radiation Therapy
Patients who undergo radiation therapy may experience some common short-term side effects (which occur in days to weeks). They include fatigue, loss of appetite and nausea. Skin rashes and hair loss often also occur over substantial regions of the scalp. Delayed side effects (occurring within months to years) can include varying degrees of memory loss and impairment of reasoning or thinking. More rarely, patients can experience impairment of pituitary function or radiation necrosis (a collection of dead tumor cells and scar tissue). Radiation necrosis can produce symptoms that are often very similar to the initial tumor presentation and include severe headache, motor weakness, visual problems or seizures.