Patterns of failure in intracranial astrocytomas after irradiation: analysis of dose and field factors.

The choice of tumor dose and treatment volume are the two most important radiation factors influencing survival in glioblastomas. Patients treated to their whole brain survive longer than those treated with limited fields. Glioblastomas treated with over 5,000 rads (1,300 rets) survive longer than those treated with smaller doses. Other factors affecting survival are: the pathological grade; age at diagnosis; and surgical treatment performed. Failure patterns in glioblastomas represent intrinsic qualities of the tumor, the host, and the treatment employed. They dictate the strategy to follow. Perhaps some of these are unaffected by irradiation. An increase in dose and the extension of fields in glioblastomas have produced a gain in both the quantity and the quality of survival. The whole brain is treated (5,000-6,000 rads) and the target volume is boosted to 7,000 to 8,000 rads. Grade II astrocytomas perhaps should be treated with whole brain irradiation (4,500 rads) and a boost to the target volume of an additional 1,000 rads.