Astrocytoma Health Article

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 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 team

Treatment of astrocytoma will involve a neurosurgeon to remove the tumor, a neuropathologist to examine the tumor sample, and an oncologist to monitor the patient's health and coordinate radiation therapy and chemotherapy if necessary. Nurses and radiation therapists will also play a role. After treatment, the patient may be followed up by a neurologist to ensure that the tumor does not grow or recur.

Clinical staging, treatments, and prognosis

There are several different systems for staging astrocytomas. The World Health Organization (WHO) system is the most common; it has four grades of increasing severity based on the appearance of the astrocytoma cells. Other methods of staging correspond fairly closely to the WHO system. Grades I and II are sometimes grouped together and referred to as low-grade astrocytomas. Over time, tumors may progress from a low-grade form with a relatively good prognosis to a higher grade form and poorer prognosis. Additionally, tumors may recur at a higher grade.

Grade I Pilocytic Astrocytoma

This is also sometimes referred to as juvenile astrocytoma because it occurs more frequently in children than adults. Under a microscope, the astrocytes are thin and elongated, and known as pilocytes. They are accompanied by Rosenthal fibers. The tumor mass does not invade surrounding tissues and is sometimes enclosed in a cyst. In children, pilocytic astrocytoma often occurs in the cerebellum, but may also occur in the cerebrum.

Treatment of this grade depends on the patient's age and the location of the tumor. Surgery is the preferred treatment for this type of astrocytoma; it is performed by a procedure known as a craniotomy. An incision is made in the skin and an opening is made in the skull. After the tumor is removed, the bone is normally replaced and the incision closed. The neurosurgeon may also insert a shunt (drainage system) to relieve intracranial pressure; this involves inserting a catheter into a cavity inside the brain called a ventricle, then threading the other end under the skin to a drainage area where the fluid is absorbed.

If the tumor can be completely surgically removed, the patient may not need further therapy and may be monitored only for recurrence. If the tumor cannot be completely removed, patients may be given chemotherapy as well. If the tumor is not completely resected or if it continues to grow after chemotherapy, radiation therapy may be necessary. Radiation therapy is not normally given to children under the age of three in order to prevent permanent damage to the child's healthy brain tissue. Radiation treatment may cause swelling in the brain; steroids may be prescribed to reduce the swelling.

The best indicator for prognosis is complete removal of the tumor. With complete tumor removal, 80% of patients are alive ten years later. Location of the tumor in the cerebellum also suggests a better prognosis than other locations.

Grade II Low-Grade Diffuse Astrocytoma

These astrocytomas spread out and invade surrounding brain tissues but grow very slowly. Under the microscope, fibrous structures are present. Grade II astrocytomas may occur anywhere in the brain, in the cerebellum and brain stem, or in the cerebrum, including the optic pathways. Genetic studies indicate that mutations of the tumor suppressor gene p53 occur frequently in these tumors.

Surgical removal of the tumor is the first choice for treatment, but it may not be possible due the tumor's location. Surgery is usually followed by radiation. Patients under 35 years of age have a better prognosis than older patients; in older patients, low-grade tumors progress to higher grades more rapidly. Overall median survival is four to five years.

Pleimorphic xanthoastrocytoma, a tumor originating in cells of a mixture of glial and neuronal origin, is often considered a grade II astrocytoma. It is relatively benign and treated only with surgery.

Grade III Anaplastic Astrocytoma

Anaplastic astrocytoma occurs most frequently in people aged 50 to 60. The term anaplastic means that the cells are not differentiated; they have the appearance of immature cells and cannot perform their proper functions. Researchers believe this is due to a gradual accumulation of genetic alterations in these cells. These tumor cells invade surrounding healthy brain tissue.

Anaplastic astrocytomas may be inoperable because of their location and their infiltration into normal tissue; in this case radiation therapy is recommended. Chemotherapy may include various combinations of alkylating agents and other drugs, including carmustine, cisplatin, lomustine, procarbazine and vincristine. These tumors tend to recur more frequently than grade I and II tumors. Following treatment, median survival is 12 to 18 months. The five-year survival rate for these patients is approximately 10% to 35%.

Grade IV Glioblastoma Multiforme

Glioblastoma Multiforme (GBM) is the most common primary brain tumor in adults. These tumors aggressively invade adjacent tissue and may even spread throughout the central nervous system. They frequently occur in the frontal lobes of the cerebrum. Tumor biopsies may show large areas of necrosis, or dead cells, surrounded by areas of rampant growth. There may also be a mixture of cell types within the biopsy. Genetic studies show that a number of different types of mutations can take place in genes for tumor suppressor p53 and other proteins that play a role in controlling the normal growth of cells.

Often GBM cannot be entirely surgically removed because it affects large areas of the brain. Radiation therapy will be given regardless of whether surgery is possible, except to very young children. Conventional radiation may be performed, but more specialized types, such as stereotactic radiosurgery, which uses imaging and a computer to treat the tumor very precisely, or interstitial radiation, which delivers radiation by placing radioactive material directly on the tumor, may also be used. Chemotherapy will follow radiation; it may include carmustine, lomustine, procarbazine, and vincristine.

GBM is most common in patients over 50 years of age and rarely occurs in patients under 30. Increasing age is associated with a poorer prognosis. Median survival is 9 to 11 months following treatment. Fewer than 5% of patients are alive five years later. Because of the poor prognosis of GBM, it is treated more aggressively than low-grade astrocytomas; many clinical trials take place to test new treatments.

Alternative and complementary therapies

While no specific alternative therapies have become popular for this particular type of brain cancer, patients interested in pursuing complementary therapies should discuss the idea with their doctor. A doctor may be able to provide information about the efficacy of certain techniques and whether they may interfere with conventional treatment.