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glioma
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Gliomas are primary tumors that occur in the brain
and central nervous system (CNS). Primary tumors
are those that originate in a specific location, such as the brain,
lungs, or breast. When primary tumors spread to other areas of
the body, they are referred to as metastatic tumors.
The term glioma refers to any primary
tumor that arises from glial cells in the brain and central
nervous system. Glial cells are non-neuronal cells that have various
roles (depending on type and location) in supporting neuronal
function.
Gliomas are a relatively rare form of cancer. Primary
CNS tumors occur in approximately 6.4% per 100,000 people; 51%
of these are glial tumors. ,
Symptoms of glioma vary according to location in
the brain or CNS, and the severity of the tumor. In general, they
are similar to those of other brain tumors and may include:
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Headaches |
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Seizures |
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Difficulty speaking |
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Inability to concentrate or think
clearly |
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Memory problems |
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Personality changes |
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Loss of balance or weakness in
part of the body |
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Vision disturbances |
Because symptoms of glioma can be non-specific and
suggestive of numerous conditions, diagnosis is usually made in
steps. Initially, patients are examined neurologically. If findings
suggest or do not rule out a possible brain tumor, the brain will
be scanned using MRI, CT, or PET. If a tumor or tumors are seen
in the scan, a biopsy or resection is usually performed. This
may be done during surgery to remove or de-bulk the tumor, or
as a closed procedure using a needle to aspirate a sample of the
tumor.
There are several different types of gliomas,
ranging from benign and slow growing to malignant and highly aggressive
tumors that spread rapidly throughout the brain. Glial tumors
are typically described by the cell of origin and further classified
by grade, or degree of aggressiveness. Common categories by cell
of origin include:,
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Astrocytoma
– tumor arising from astrocytes |
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Oligodendroglioma
– tumor arising from oligodendrocytes |
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Ependymoma –
tumor arising from ependymal cells |
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Mixed glioma
– tumor arising from a mixture of astrocytes and oligodendrocytes |
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Ganglioglioma
– tumor arising from both glial cells and neurons |
Among the many glioma tumor types, astrocytomas
are the most common. Astrocytomas are graded according to their
pathologic features and aggressiveness, which determines the prognosis
and treatment.
I – Pilocytic astrocytoma
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Very slow-progressing,
encapsulated tumor |
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Treated surgically, with full
or partial removal |
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Partially removed tumors are also
treated with radiation and sometimes chemotherapy |
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Often curable with treatment |
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Occurs primarily in children |
II – Low-grade (diffuse) astrocytoma
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Slowly-progressing
tumor |
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Treated with full or partial surgical
removal when possible |
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Inoperable, partially removed,
or recurrent tumors are often treated with radiation; the
addition of chemotherapy is being studied |
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Prognosis is good with treatment |
III – Anaplastic astrocytoma
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Malignant, rapidly-progressing
tumor that often
spreads to other areas of the CNS |
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Treatment involves surgery (when
possible) followed by radiation and usually chemotherapy |
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Cure rate is low with standard
treatment |
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Studies are currently evaluating
combinations of radiation and various chemotherapies and biologics
in recurrent or inoperable anaplastic tumors |
IV – Glioblastoma multiforme
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Highly invasive, rapidly
growing tumor that can
spread throughout the brain |
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May develop de novo or evolve
from lower-grade astrocytomas or oligodendrogliomas |
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Treatment involves surgery (when
possible) followed by radiation and usually chemotherapy |
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Studies are currently evaluating
combinations of radiation and various chemotherapies and biologics
in recurrent or inoperable glioblastomas |
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Cure rate is very low; median
time of survival from time of diagnosis is approximately one
year |
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Most common form of glial tumor
in adults; occur somewhat more frequently in men than women |
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H and E stained section
demonstrates a collection of large irregularly-shaped tumor
cells occurring in the center of a field of more bland-appearing
neuropil. |
Oligodendrogliomas make up about 5% of all gliomas,
and occur as two different types: Grade II and Grade III.
Grade II oligodendrogliomas are usually well defined
and relatively responsive to treatment; treatment includes surgery,
radiation and chemotherapy.
Grade III (anaplastic) oligodendrogliomas
are typically diffuse and invasive tumors. They generally respond
less favorably to treatment than grade II oligodengliomas. However,
a subset of tumors associated with a particular chromosomal abnormality
(an allelic loss of 1p and/or 19q) seem to respond more favorably
to therapy, which would include radiation and/or chemotherapy.
Ependymomas make up about 5% of gliomas in
adults and 10% of gliomas in children. Most ependymomas are slow
growing, benign and respond to surgery and/or radiation therapy.
In about 15% of cases, ependymomas are malignant and require surgery,
radiation and chemotherapy.
Mixed gliomas involve both astrocytes and oligodendrocytes.
Mixed gliomas range from low-grade and slow-progressing to high-grade
and malignant. Treatment and prognosis depend on the grade of
the tumor. In general, mixed gliomas are treated according to
recommended treatment for the most aggressive component of the
tumor. Prognosis for high grade mixed gliomas is poor compared
to low grade mixed gliomas.
Gangliogliomas are the rarest form of glioma. They
are generally benign, slow-growing tumors that affect both glial
and neuronal cells in the brain and/or spinal cord. Gangliogliomas
usually respond well to surgical removal.
More information about gliomas and other primary
brain tumor types can is available at The
National Cancer Institute.
For information about ongoing clinical trials
evaluating  I-TM-601
in patients with high-grade glioma, click
here.
References:
1. Surveillance, Epidemiology, and End Results
(SEER) Program (www.seer.cancer.gov) Public-Use Data (1973-2003),
National Cancer Institute, DCCPS, Surveillance Research Program,
Cancer Statistics Branch, released April 2006, based on the November
2005 submission. Available at: http://seer.cancer.gov/publicdata/.
Accessed 8/06.
2. Hess KR, Broglio KR, Bondy ML. Adult glioma
incidence trends in the United States. 1977-2000. Cancer. 2004;101:2293-2299.
3. Adult Brain Tumors: Treatment (PDQ®).
National Cancer Institute. Available at: http://www.cancer.gov/cancertopics/pdq/treatment/adultbrain/healthprofessional.
Accessed 8/06.
4. Diagnosis and treatment. National Brain
Tumor Foundation. Available at: http://www.braintumor.org/patient_info/surviving/.
Accessed 8/06.
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