Glioma

Glioma

[glahy-oh-muh]
A glioma is a type of cancer that starts in the brain or spine. It is called a glioma because it arises from glial cells. The most common site of gliomas is the brain.

Classification

Gliomas are classified by cell type, by grade, and by location.

By type of cell

Gliomas are named according to the specific type of cell they most closely resemble. The main types of gliomas are:

By grade

Gliomas are further categorized according to their grade, which is determined by pathologic evaluation of the tumor.

  • Low-grade gliomas are well-differentiated (not anaplastic); these are benign and portend a better prognosis for the patient.
  • High-grade gliomas are undifferentiated or anaplastic; these are malignant and carry a worse prognosis.

Of numerous grading systems in use, the most common is the World Health Organization (WHO) grading system for astrocytoma. The WHO system assigns a grade from 1 to 4, with 1 being the least aggressive and 4 being the most aggressive. Various types of astrocytomas are given corresponding WHO grades.

WHO grading system for astrocytomas
*WHO Grade 1 — e.g., pilocytic astrocytoma
*WHO Grade 2 — e.g., diffuse or low-grade astrocytoma
*WHO Grade 3 — e.g., anaplastic (malignant) astrocytoma
*WHO Grade 4 — glioblastoma multiforme (most common glioma in adults)

The prognosis is the worst for grade 4 gliomas, with an average survival time of 12 months. Overall, few patients survive beyond 3 years.

By location

Gliomas can be classified according to whether they are above or below a membrane in the brain called the tentorium. The tentorium separates the cerebrum, above, from the cerebellum, below.

  • supratentorial: Above the tentorium, in the cerebrum, mostly in adults (70%). Senator Edward M. Kennedy’s brain tumor, for example was supratentoral, in the parietal area in the upper part of the left side of his brain, above the ear.
  • infratentorial: Below the tentorium, in the cerebellum, mostly in children (70%)

Symptoms

Symptoms of gliomas depend on which part of the central nervous system is affected. A brain glioma can cause headaches, nausea and vomiting, seizures, and cranial nerve disorders as a result of increased intracranial pressure. A glioma of the optic nerve can cause visual loss. Spinal cord gliomas can cause pain, weakness, or numbness in the extremities. Gliomas do not metastasize by the bloodstream, but they can spread via the cerebrospinal fluid and cause "drop metastases" to the spinal cord.

Pathology

High-grade gliomas are highly-vascular tumors and have a tendency to infiltrate. They have extensive areas of necrosis and hypoxia. Often tumor growth causes a breakdown of the blood-brain barrier in the vicinity of the tumor. As a rule, high-grade gliomas almost always grow back even after complete surgical excision.

On the other hand, low-grade gliomas grow slowly, often over many years, and can be followed without treatment unless they grow and cause symptoms.

Prognosis

Gliomas cannot be cured. The prognosis for patients with high-grade gliomas is generally poor, and is especially so for older patients. Of 10,000 Americans diagnosed each year with malignant gliomas, about half are alive 1 year after diagnosis, and 25% after two years. Those with anaplastic astrocytoma survive about three years. Glioblastoma multiforme has a worse prognosis.

Treatment

Standard therapy

Treatment for brain gliomas depends on the location, the cell type and the grade of malignancy. Often, treatment is a combined approach, using surgery, radiation therapy, and chemotherapy. The radiation therapy is in the form of external beam radiation or the stereotactic approach using radiosurgery. Spinal cord tumors can be treated by surgery and radiation. Temozolomide is a chemotherapeutic drug that is able to cross the blood-brain barrier effectively and is being used in therapy.

Refractory disease

For recurrent high-grade glioblastoma, recent studies have taken advantage of angiogenic blockers such as bevacizumab in combination with conventional chemotherapy, with encouraging results.

Experimental therapies

The use of oncolytic viruses or gene therapy using prodrug converting retroviruses and adenoviruses is being studied for the treatment of gliomas.

The experimental cancer medicine "Ukrain" has been used for solid cancers. There are case reports of efficacy on gliomas .

5-aminolevulinic acid, a drug that makes certain cells, including gliomas, fluorescent, has been used to make surgical removal of gliomas more effective by making it easier to identify and remove them during surgery..

Boron neutron capture therapy.

Notable cases

References

External links

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