Astrocytomas represent a complex group of benign and malignant cerebral tumors arising at any age.
They are the most frequent cerebral tumors and represent more than half of all primary brain tumors. Incidence is estimated at 1/12,500.
The most frequent benign tumors are juvenile pilocytic astrocytomas (grade I) and diffuse low grade or fibrillary astrocytomas (grade II). The most frequent malignant tumors include anaplastic astrocytomas (grade III), glioblastomas (grade IV, the most severe form of astrocytoma; see this term), giant cell glioblastomas and gliosarcomas. Pleomorphic xanthoastrocytomas can be malignant or benign. These tumors occur at all ages although glioblastomas are more frequent in adults and in elderly people, while pilocytic astrocytomas are more frequent in children and adolescents. Age at diagnosis may influence tumor biology and evolution; the outcome generally being better in children. Speed of tumor growth is related to tumor grade. Symptom duration of less than three months is usually seen with malignant tumors.
Apart from cranial irradiation, which may itself induce glioblastomas, the underlying causes of these tumors are not known. The principal genetic predisposing syndromes are: neurofibromatosis type 1, Turcot syndrome and Li-Fraumeni syndrome (see these terms). Familial cases of isolated astrocytomas are very rare.
Diagnosis is made after MRI, which reveals an intraparenchymal lesion associated with a mass effect and compression of the normal structures.
Treatment first consists of surgery, which aims at removing as much of the tumor as possible. If complete, surgical resection may be the only treatment required for benign astrocytomas. Adjuvant treatment is required for malignant tumors, whatever the quality of the resection. In case of incomplete resection of a benign tumor, adjuvant treatment may also be discussed. Radiation therapy is usually used in adults and in children over 10 years of age. Chemotherapy is preferred for younger children and may even be discussed for adults. The most chemosensitive tumors are pilocytic astrocytomas and anaplastic astrocytomas. Pilocytic tumors are highly curable, while malignant tumors are often fatal. The neurologic and intellectual sequelae of these tumors and their treatment may be severe, especially in young children, elderly people and patients requiring extended irradiation. Patient management requires multidisciplinary teams with expertise in the field of brain neoplasms. The relative rarity of these tumors calls for the management of patients in prospective trials aimed at improving prognosis and quality of survival.
Prognosis depends on tumor histology (benign or malignant) and location (operable or not).
Last update: November 2007