Gliomas

Gliomas are tumors that start in the brain or spine. Three types of normal glial cells can produce tumors: astrocytes, oligodendrocytes and ependymal cells. The tumors are named after the normal cells from which they are derived as well as what they look like under a microscope: 


Astrocytomas
Astrocytomas are made up of astrocytes — star-shaped cells that form the supportive, glue-like tissue of the brain. The cells are graded on a scale of 1 to 4 (the terminology I to IV is also used) according to how normal or abnormal they appear. They are also referred to as either low grade or high grade.
  
  • Low-grade astrocytomas (grades 1 and 2) are usually slow growing and localized to one area. Among children who have astrocytomas, most are low grade.
  • High-grade astrocytomas (grades 3 and 4) grow quickly and require different treatment. Most astrocytoma tumors in adults are high grade.

Astrocytomas appear in different parts of the brain and nervous system, including the brain stem and spinal cord. 

Pilocyctic Astrocytoma 
Pilocytic astrocytomas are low-grade tumors that are most often found in children and young adults. They have a tendency to arise in the cerebellum, the part of the brain that controls balance, and they can form areas with cysts (pockets of fluid). Pilocytic astrocytomas have sharply defined boundaries, which is why they are often curable with surgery when located in an accessible part of the brain. Radiation or chemotherapy are generally used to treat inaccessible or partially removed tumors.

Even though they are considered benign, these tumors can cause significant neurologic symptoms even after surgical resection, which is usually the only treatment offered. These tumors can recur, but rarely become malignant, invading surrounding tissue and/or travel to other sites. If they recur, treatment may include additional surgery, radiation or chemotherapy.

Pleomorphic Xanthoastrocytomas 
Pleomorphic xanthoastrocytomas, also referred to as PXAs, are low-grade tumors that most commonly occur in children and tend to be located near the surface of the brain. As with pilocytic astrocytomas, surgery is the primary treatment.

Diffuse Astrocytomas
Diffuse astrocytomas are the most common type of low-grade astrocytomas. These tumors include fibrillary, gemistocytic and protoplasmic astrocytomas, which refer to the characteristics of the cells they contain. They often contain microcysts and mucous-type fluid, are slower growing and are typically less aggressive than other astrocytomas, but tend to invade surrounding areas. They most often occur in the cerebral cortex, often referred to as the thinking/conscious part of the brain.

Over time, these tumors can become more aggressive and can turn into anaplastic astrocytomas or glioblastomas. The challenge in treating diffuse astrocytomas is to use the most effective treatment to prevent or delay them from becoming malignant, while minimizing the toxic effects of treatments.

Sometimes the tumor can be completely removed with surgery. Radiation and/or chemotherapy may be used early on, or used exclusively if the tumor cannot be removed with surgery. This type of treatment may also be used if the tumor recurs. Every patient’s situation is different. At Houston Methodist, we use pathologic information and specific genetic testing to help guide our treatment plan for diffuse astrocytoma.

Anaplastic Astrocytoma 
Anaplastic astrocytomas (AAs) are grade 3 tumors, which are more aggressive than diffuse astrocytomas, but less aggressive than primary glioblastoma. These rare tumors require an integrated, aggressive treatment plan because their tentacle-like projections invade surrounding tissue and make them difficult to remove with surgery alone.

Typically, treatment begins with surgery to remove as much of the tumor as safely as possible without causing new neurological problems. This is usually followed with radiation, then chemotherapy involving monthly temozolomide.

Anaplastic astrocytomas have a high chance of recurrence, and can return in the form of a more malignant glioblastoma. If this happens, our doctors and scientists will review the previous treatments to determine the best course of action to treat the recurrence.

Glioblastomas
Glioblastomas are a type of astrocytoma made up of transformed normal brain cells called astrocytes. This makes it easy for them to invade and thrive in normal brain tissue.

Glioblastomas (also known as grade-4 astrocytoma and glioblastoma multiforme) are the most common types of malignant (cancerous) primary brain tumors. They are extremely aggressive for a number of reasons. First, glioblastoma cells multiply quickly, as they secrete substances that stimulate a rich blood supply. They also have an ability to invade and infiltrate long distances into the normal brain by sending microscopic tendrils of tumor alongside normal cells. In a sense, these tumors are like an octopus, with a head composing the main tumor mass, and tentacles that extend long distances outwards.

There are two types of glioblastomas.

  • Primary glioblastoma are the most common form; they grow quickly and often cause symptoms early.
  • Secondary glioblastomas are less common, accounting for about 10 percent of all glioblastomas. They progress from low-grade diffuse astrocytoma or anaplastic astrocytoma, and are more often found in younger patients. Secondary glioblastomas are preferentially located in the frontal lobe and carry a better prognosis. 

Glioblastomas usually require a combined treatment plan. First, as much tumor as possible is removed during surgery. The tumor’s location in the brain often determines how much of it can be safely removed. After surgery, radiation and chemotherapy slow the growth of remaining tumor cells. 

The oral chemotherapy drug, temozolomide, is most often used for six weeks, and then monthly thereafter. It has fewer side effects than many other forms of chemotherapy. Another drug, bevacizumab (known as Avastin®), may also be used during treatment. This drug attacks the tumor’s ability to recruit blood supply, often slowing or even stopping tumor growth. 

In addition to this standard therapy, the doctors at Houston Methodist offer novel investigational treatments that strive to find better ways of treating glioblastoma. This may involve adding treatments to the standard therapy or replacing one part of the standard therapy with a different treatment that may work better. We offer investigational treatments through multicenter trials (studies involving other research institutions), as well as a number of options that are unique to the Kenneth R. Peak Center for Brain and Pituitary Tumor Treatment and Research Center.

The latest innovative option is Optune™, a non-invasive treatment for glioblastoma patients that delivers low-dose pulses of electricity to the area of the brain where the tumor exists. Click here to learn more about this unique treatment for glioblastoma.

Gangliogliomas
Gangliomas are a mixed-cell tumor (composed of two different cell types):

  • Cancerous glial cells (most often derived from astrocytes)
  • Nerve cells (mature ganglion cells) 

Gangliogliomas are very rare, accounting for just one percent of all brain tumors. However, they account for about 10 percent of brain tumors in children. 

Most gangliogliomas are benign (noncancerous), slow-growing, low-grade tumors. They can affect the central nervous system, and are often associated with epilepsy (seizures). In about 10 percent of ganglioglioma cases, the tumors can grow more quickly, spread and become malignant (cancerous).

Gangliogliomas are often treated successfully with surgery only. However, if cells remain or the tumor recurs, additional surgery, radiation, and/or chemotherapy may be used.

Oligodendrogliomas 
Oligodendrogliomas come from the cells that are responsible for making myelin, the insulating substance that forms on the outside of many nerve cells. They may contain calcifications, hemorrhage (bleeding areas), and/or cysts. Sometimes they are mixed with other types of glia, or supporting brain cells. Only four percent of brain tumors are oligodendrogliomas, and they occur most often in adult men 50 to 60 years of age.

Oligodendrogliomas can be low grade or high grade (generally grade 2 or 3), according to how the cells appear and how quickly they spread. A biopsy is typically performed to confirm the diagnosis, determine the grade of tumor and guide treatment plans:
  
  • Grade 2 oligodendrogliomas are low-grade tumors, often successfully removed with surgery. Radiation treatment may be needed to treat any remaining tumor cells. 
  • Grade 3 and recurrent oligodendrogliomas are usually treated with a combination of radiation and chemotherapy. 

Over time, oligodendrogliomas can recur and become more aggressive. We use pathologic information and specific genetic testing to help guide our treatment plan for each patient’s specific situation.

Ependymomas
Ependymomas are brain tumors that develop from the cells that line the ventricles and other fluid-filled cavities of the brain and spinal cord, and may contain cysts or calcifications. Although ependymomas are somewhat rare among adults, making up just two to three percent of adult primary brain tumors, they are the sixth most common brain tumor among children. About one-third of pediatric ependymomas occur in children under age three.

There are four main types of ependymomas, ranging from low- to high grade.
  
  • Subependymomas are slow-growing grade 1 tumors that tend to grow near a ventricle.
  • Myxopapillary ependymomas are slow-growing grade 1 tumors that tend to grow in the lower part of the spine.
  • Grade 2 ependymomas are the most common ependymal tumors and include four subtypes: cellular, papillary, clear cell and tancytic ependymomas. These tend to grow along, within or next to the ventricular system.
  • Anaplastic ependymomas are usually fast-growing grade 3 tumors. In adults, they usually grow in the brain. In children, they are usually found in the posterior fossa (lower back part of the skull).

Low-grade ependymomas are often treated only with surgical resection. High-grade tumors are treated with a combination of surgery, radiation, and/or chemotherapy. As with any brain tumor, there is a risk that they can recur, and low-grade ependymomas could become high grade. If it recurs, repeated surgery, radiation or chemotherapy is considered. 

Additional information is available to help you learn more about glioma brain tumors:


TREATMENT LOCATIONS

Our physicians at Houston Methodist specialize in treating brain tumors at the following convenient locations.