Grade 4: Grade 4 astrocytomas, frequently referred to as glioblastomas or glioblastoma multiforme, are the most malignant variety of these tumors. They are made up of cells which infiltrate brain tissue with a region - in some cases, multiple regions - of solid tumor tissue within the zone of infiltrated brain tissue. Mitoses are frequently noted by the pathologist as the surgical specimen is examined. In addition, regions of necrosis (dead tissue) are also noted where the tumor has grown so fast that parts of it has outpaced its blood supply. These tumors induce the formation of new but abnormal blood vessels. The identification of these blood vessels are also important in establishing the diagnosis. The CT and MRI demonstrate a contrast enhancing mass with a hypodense center (corresponding to necrosis), surrounded by a zone of hypodensity on CT and prolonged T1 and T2 on MRI (corresponding to infiltrated parenchyma).
The Grade 4 astrocytoma has the worst prognosis of all: 17 weeks average (mean)survival after diagnosis without treatment; 30 weeks average survival with biopsy followed by radiation therapy; 37 weeks average survival following surgical removal of most of the tumor tissue component of the tumor and radiation therapy; and 51 weeks average survival following stereotactic volumetric resection of the tumor tissue component and radiation therapy.
The prognosis for any patient with a malignant astrocytoma (Grade 3 or 4) is also very dependent upon age (older people do not live as long as young patients) and performance status (patients who are neurologically normal and independent live longer than patients who have a neurological deficit). Chemotherapy has been shown to add several weeks to survival. Radiation implants(brachytherapy) have also been shown to increase survival but more than half of these patients require another operation to remove dead tissue resulting from the radiation.