What is an astrocytoma?
An astrocytoma is a brain tumor made up of astrocytes, which are glial cells that support the neurons of the brain. Astrocytomas are the most common type of primary brain tumors originating from brain tissue. There are approximately 12,000 new cases of astrocytoma every year. Even the most aggressive astrocytomas almost never spread throughout the blood and lymphatic systems into other parts of the body, and in this sense they differ from cancers in that they typically remain confined to the central nervous system.
Among astrocytomas, there is a spectrum of how malignant or aggressive a tumor can be. The World Health Organization (WHO) grades astrocytomas from I-IV, with IV being the most aggressive and infiltrative astrocytoma called glioblastoma multiforme (GBM). WHO Grade III astrocytomas are also known as anaplastic astrocytoma (AA). WHO Grade II astrocytomas are also known as low grade, or diffuse astrocytoma. WHO Grade I tumors comprise a separate entity, consisting of various (often benign) tumors usually seen in the pediatric populations. The most common of these are pilocytic astrocytomas (WHO Grade I), which usually have a very good prognosis following complete surgical removal.
Although they do not metastasize like malignant cancers, astrocytomas are not "benign" because they may infiltrate or invade the brain tissue, even beyond the areas they are visualized on imaging studies such as MRI. Cells from the tumor may spread into and mix themselves among normal brain cells. With the naked eye, or even under an operating microscope, it is often not possible to differentiate normal from infiltrated brain. It is only with the neuropathologists high-power microscope magnifying 25 to 40 times that abnormal tumor cells can be seen as they mix in with normal brain tissue. At the current time, it is not possible to obtain a cure of an infiltrative or high-grade astrocytoma (Grade III or IV). This implies that other treatment approaches, such as chemotherapy and radiation, are needed to control these tumor types. In addition, numerous experimental clinical trials are available at USC for patients with newly diagnosed and recurrent astrocytomas.
What causes astrocytomas?
The cause of an astrocytoma is unknown. Although the initial cause is thought to be related to mutations in the DNA of the tumor cells, there are currently no clear-cut environmental or behavioral risk factors (such as air pollution or smoking) that are known to cause astrocytomas.
What are the symptoms of an astrocytoma?
Common presenting signs and symptoms of astrocytomas include headache, seizures, weakness, nausea, and visual complaints. The first symptom of a brain tumor of any type can be a headache. The reason that patients get headaches with brain tumors is that these masses cause increased pressure in the brain. The headache associated with a brain tumor is frequently worse in the morning and may be associated with nausea or vomiting. Other symptoms of a brain tumor can include seizures, weakness or numbness of a side or part of the body, or even such subtle symptoms such as changes in mood, memory, thinking or general state of well-being. Sometimes increased pressure in the brain can cause blurred, double or loss of vision.
What do I do if I have these symptoms?
If a patient has any of the symptoms mentioned above with no other obvious explanation a diagnostic work-up should be done. Astrocytoma, like other brain tumors, is currently best seen on magnetic resonance imaging (MRI) studies of the brain. Computerized tomography (CT) is also a good technique for seeing structures in the head and brain but does not show quite as much detail, as does MRI. The problem with MRI is that while it is a good technique for detecting a brain mass, it does not identify the type of mass. An astrocytoma can look like other kinds of brain tumor, or even like an infection. A biopsy is needed to confirm the diagnosis of astrocytoma and also to grade the tumor, in order to guide the next steps of appropriate treatment and provide a prognosis for survival time. The microscopic structure of an astrocytoma is extremely important in making decisions about treatment and in predicting survival. On the basis of features of cells within tumors, neuropathologists can often predict how aggressively a tumor will behave, and assign a WHO grade, which ultimately contributes to how long a patient will survive and what quality of life they may have.
What is the treatment?
The treatment of an astrocytoma depends tremendously on the tumor WHO grade and subtype, as well as size and location of the tumor. Through many decades of research, we have learned that for most astrocytomas, the amount of tumor removed may correlate with survival time. At the same time, for higher grade (WHO Grade III and IV) astrocytomas, although all visible portions of the tumor may be removed with surgery, the tumor has often already infiltrated the surrounding brain far beyond the margins of the visible tumor, making a surgical cure impossible.
Treatment for astrocytomas can be surgical or non-surgical. One of the key principles we focus on is maximal tumor removal with preservation of quality of life and neurological function. To maintain this standard, we offer the most advanced, state-of-the-art, surgical techniques for glioma removal, including:
- Neurophysiological monitoring
- Standard Motor Mapping
- Advanced neuro-imaging (functional MRI, MR perfusion, tractography, spectroscopy)
- Intraoperative MRI
- Awake speech and motor mapping
- Neuro-navigation technology
The primary non-surgical treatment is radiation. Radiation can be administered to the whole brain, or it can be relatively focused to a selected region of the brain via a technology called radiosurgery. USC offers the benefits of several types of radiosurgery, including Gamma Knife and Cyberknife, both of which allow very precise focusing of radiation beams into the area of astrocytoma with minimized damage to surrounding brain. All forms of radiation therapy, however, are still associated with particular risks that must be considered prior to administration.
Chemotherapy is another option for treatment of astrocytomas. The current standard of therapy for newly-diagnosed high grade astrocytomas (WHO Grade III or IV) typically include 6 weeks of chemotherapy using a drug called temozolamide, in conjunction with radiation therapy. Following this, many patients will have the option of enrolling in a major clinical trial, typically investigating an experimental intervention for treating these tumors.
In addition, the Department of Neurosurgery and Neuro-Oncology Program at USC/Norris Cancer Center is currently carrying out numerous research projects to investigate many aspects of astrocytomas and various treatments. Many patients that have surgery at USC have their brain tumors freshly frozen, so that future genetic or molecular studies can be done to analyze them or even potentially customize a tailored treatment option for patients, should a new therapy become available.