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Astrocytoma
Classification and external resources
Two PET images — the above of which shows a normal brain and the below shows astrocytoma.
ICD-10	C71.
ICD-9	191
ICD-O:	M9400/3
OMIM	137800
DiseasesDB	29449
eMedicine	med/2693

Astrocytomas are neoplasms of the brain that originate in star-shaped brain cells called astrocytes. This type of tumor doesn't usually spread outside the brain and spinal cord and it doesn't usually affect other organs. Astrocytomas are the most common glioma, and can occur in most parts of the brain and occasionally in the spinal cord. Astrocytomas originate from cells called astrocytes and are most commonly found in the main part of the brain, the cerebrum. People can develop astrocytomas at any age, but they are more prevalent in adults. Astrocytomas in the base of the brain are more common in young people. They account for roughly 75% of neuroepithelial tumors.^{[citation needed]}

Grading

Of numerous grading systems in use for the classification of tumor of the central nervous system, the World Health Organization (WHO) grading system is commonly used for astrocytoma. Established in 1993 in an effort to eliminate confusion regarding diagnoses, the WHO system established a four-tiered histologic grading guideline for astrocytomas that 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 these WHO grades:

• WHO Grade 1- Consist of pilocytic astrocytomas, pleomorphic xanthoastrocytomas, subependymal giant cell astrocytomas, and subependymomas are uncommon tumors, but can often be cured by surgically removing the tumor. Even if the surgeon is not able to remove the entire tumor, it may remain inactive or be successfully treated with radiation.

• WHO Grade 2- Consist of oligodendrogliomas, astrocytomas, mixed oligoastrocytomas. They are prevalent in younger people who are often present with seizures. Median survival varies with the cell type of the tumor. Grade 2 astrocytomas are defined as being infiltrative gliomas, meaning that the tumor cells penetrate into the surrounding normal brain, making a surgical cure more difficult. People with oligodendrogliomas have better prognoses than those with mixed oligoastrocytomas, who in turn have better prognoses than patients with astrocytomas. Other factors which influence survival include age (younger the better) and performance status (ability to perform tasks of daily living). Due to the infiltrative nature of these tumors, recurrences are relatively common. Depending on the patient, radiation or chemotherapy after surgery is an option.

• WHO Grade 3- Consist of just anaplastic astrocytoma. It is often presented with seizures, neurologic deficits, headaches, or changes in mental status. The standard initial treatment is to remove as much of the tumor as possible without worsening neurologic deficits. Radiation therapy has been shown to prolong survival and is a standard component of treatment. In general, median survival ranges from two to three years. There is no proven benefit to adjuvant chemotherapy or supplementing other treatments for this kind of tumor. Although temozolomide is effective for treating recurrent anaplastic astrocytoma, its role as an adjuvant to radiation therapy has not been fully tested.

• WHO Grade 4-Consists of Glioblastoma multiforme (GBM), which is the most common and most malignant primary brain tumor. Glioblastoma multiforme usually spreads quickly to other parts of the brain. For this reason, these tumors are difficult to treat, and it is common for them to recur after initial treatment. This tumor can occur in all age groups, including children; the average age at which it is diagnosed is 55 years. Symptoms often begin abruptly with seizures. Surgical removal remains the mainstay of treatment,^{[citation needed]} provided that unacceptable neurologic injury can be avoided. The extremely infiltrative nature of this tumor makes complete surgical removal impossible. Although radiotherapy rarely cures glioblastoma, studies show that it doubles the median survival of patients, compared to supportive care alone. The prognosis is worst for these grade 4 gliomas. Few patients survive beyond 3 years. Median survival of GBM victims who forgo treatment is approximately 90 days and is only extended to about twelve months by aggressive surgery, radiation and chemotherapy. Long term survival (at least five years) falls well under 3%.^[1][2]

The low grade astrocytomas (I & II) are among the least common of all reported brain tumors, less than 6%, while the highest grade (IV), GBM, is the most common primary CNS malignancy and second most frequent brain tumor. Despite the low incidence of astrocytomas compared to other human cancers, mortality is significant, as the higher grades (III & IV) present high mortality rates.

Diagnosis

A Computed Tomography (CT) or Magnetic Resonance Imaging (MRI) scan is necessary to characterize the extent of these tumors (size, location, consistency). CT will usually show distortion of third and lateral ventricles with displacement of anterior and middle cerebral arteries. Histologic analysis is necessary for grading diagnosis.

In the first stage of diagnosis the doctor will take a history of symptoms and perform a basic neurological exam, including an eye exam and tests of vision, balance, coordination and mental status. The doctor will then require a computerized tomography (CT) scan and magnetic resonance imaging (MRI) of the patient's brain. During a CT scan, x rays of the patient's brain are taken from many different directions. These are then combined by a computer, producing a cross-sectional image of the brain. For an MRI, the patient relaxes in a tunnel-like instrument while the brain is subjected to changes of magnetic field. An image is produced based on the behavior of the brain's water molecules in response to the magnetic fields. A special dye may be injected into a vein before these scans to provide contrast and make tumors easier to identify.

If a tumor is found, it will be necessary for a neurosurgeon to perform a biopsy on it. This simply involves the removal of a small amount of tumor tissue, which is then sent to a neuropathologist for examination and staging. The biopsy may take place before surgical removal of the tumor or the sample may be taken during surgery. Staging of the tumor sample is a method of classification that helps the doctor to determine the severity of the astrocytoma and to decide on the best treatment options. The neuropathologist stages the tumor by looking for atypical cells, the growth of new blood vessels, and for indicators of cell division called mitotic figures.

Treatment

For low grade astrocytomas, removal of the tumor will generally allow functional survival for many years. In some reports, the five-year survival has been over 90% with well resected tumors. Indeed, broad intervention of low grade conditions is a contested matter. In particular, pilocytic astrocytomas are commonly indolent bodies that may permit normal neurologic function. However, left unattended these tumors may eventually undergo neoplastic transformation. To date, complete resection of high grade astrocytomas is impossible because of the diffuse infiltration of tumor cells into normal parenchyma. Thus, high grade astrocytomas inevitably recur after initial surgery or therapy, and are usually treated similarly as the initial tumor. Despite decades of therapeutic research, curative intervention is still nonexistent for high grade astrocytomas; patient care ultimately focuses on palliative management.

Prevention

There are no precise guidelines because the exact cause of astrocytoma is not yet known.

Famous sufferers

Long-time U.S. Senator Ted Kennedy (D-MA) died of malignant glioma.^[3] The course of his illness suggests GBM. After his initial seizure and subsequent diagnosis in May 2008, he chose aggressive treatment and survived 15 months.

2001 World Rally Championship winner Richard Burns was diagnosed with it after suffering a blackout while traveling to the 2003 Wales Rally GB. He died on 25 November 2005, four years to the day after winning the WRC Championship

See also

• Intracranial pressure

References

"Types of Cancer Teens Get." KidsHealth - the Web's most visited site about children's health. Web. 07 Dec. 2009. [1].

"Astrocytoma - Diagnosis and Treatment Options at Mayo Clinic." Mayo Clinic: Medical Treatment and Research Centers. Web. 07 Dec. 2009. [2].

"Glioblastoma Multiforme Treatment at Mayo Clinic." Mayo Clinic: Medical Treatment and Research Centers. Web. 07 Dec. 2009. [3].

"The new WHO Classification of Tumors affecting the Central Nervous System" by Stephen B. Tatter, M.D., Ph.D.; MGH [4]

External links

• Low Grade Astrocytomas in Children, Tumor Types, Treatment, FAQs, Research