|Astrocytomas are tumors that arise from brain cells called astrocytes. Gliomas originate from glial cells, most often astrocytes. Sometimes the terms "astrocytoma" and "glioma" are used interchangeably. Here, we use "astrocytoma" to refer to these tumors as a group. Astrocytomas are of two main types--high grade and low grade. High-grade tumors grow rapidly and can easily spread through the brain. Low-grade astrocytomas are usually localized and grow slowly over a long period of time. High-grade tumors are much more aggressive and require very intensive therapy. The majority of astrocytic tumors in children are low-grade, whereas the majority in adults are high-grade. These tumors can occur anywhere in the brain and spinal cord. Common sites in children are the cerebellum (the area just above the back of the neck), cerebral hemispheres (the top part of the brain), and the thalamus or hypothalamus (located in the center of the brain).|
|Astrocytomas account for the majority of pediatric brain tumors. About 700 children are diagnosed with low-grade astrocytomas each year. In children, more than 80% of astrocytomas are low-grade; nearly 20% are high-grade.|
|Clinical features and symptoms:|
|Clinical features and symptoms depend on the location of the tumor and the child's age. The most common location is in the cerebellum. Patients with cerebellar tumors have symptoms that include headache, vomiting, and unsteadiness in walking. Tumors in the cerebral hemispheres commonly present with seizures; occasionally there is weakness of the arms and legs. Tumors in the hypothalamus often present with visual problems, while thalamic tumors cause headaches and arm or leg weakness.|
removal of the tumor (resection) is the best option for tumors in areas
where this can be done without damaging the normal, surrounding brain.
For low-grade astrocytomas that are completely removed, no further therapy
is needed. If the surgeon cannot completely remove the tumor and the child
has not finished growing, chemotherapy may be given with later, delayed
use of radiation therapy. This is done because radiation causes more long-term
side effects in younger children. Radiation therapy is used for older children
and those whose tumors keep growing despite chemotherapy. About 90% of
children with low-grade astrocytomas are alive 5 years from diagnosis.
High-grade astrocytomas can rarely be removed totally because they often affect large areas of the brain by the time symptoms are obvious. All patients with high-grade astrocytomas receive both radiation therapy and chemotherapy regardless of age. Currently, the prognosis is poor in this group of patients. The subset of patients who have high-grade tumors that can be removed have survival rates of 35% to 40% after postsurgical irradiation with chemotherapy.
for the low-grade astrocytomas focus on developing chemotherapy regimens
that control tumor growth with fewer side effects on other organs of the
body. Because these tumors grow slowly, the strategy is to give less intensive
chemotherapy over long periods of time. For older children and those whose
tumors progress despite chemotherapy, new radiation techniques are under
study to deliver more localized therapy with minimal effects on the normal
For high-grade tumors, new approaches include use of new chemotherapy drugs, high doses of chemotherapy following radiation therapy, and gene therapy to make the tumor cells more sensitive to chemotherapy. A major problem in treatment is that the high dose chemotherapy also kills cells in the bone marrow that produce healthy blood. This raises the risk of severe infection and slows down the delivery of chemotherapy. Gene therapy approaches are being developed to protect bone marrow from these side effects so that chemotherapy can be given more intensively to fight the rapid tumor growth.