Treatment of grades I and II brain astrocytomas. The role of radiotherapy.

Abstract This retrospective analysis of 68 patients with Grade I or II brain astrocytomas included the years 1958-74. Two-thirds or 45 of the 68 cases received adjuvant irradiation. Fifty-six of the 68 tumors were histologic Grade II, the remaining twelve were Grade I. Comparison of all prognostically important parameters between the 45 irradiated and 23 non-irradiated patients revealed minimal but statistically insignificant bias in favor of the "grossly" excised, Grade II, and non-irradiated cases. Cumulative life-table survivals revealed excellent 5-year results for the 22 "grossly" excised cases (90%), with progressive decline in survival rates for the 45 irradiated patients (54%), the 23 non-irradiated cases (32%), and for the 45 incompletely excised cases with (41%) or without (13%) adjuvant radiotherapy. Ten-year cumulative survivals declined to 20–30% range regardless of treatment and prognostic parameters. An important exception is the 100% survival of the seven childhood cerebellar astrocytomas. Conclusions, based on analysis of treatment data, are as follows: Incompletely excised Grade I astrocytomas require adjuvant irradiation commensurate to Grade II lesions. Irradiation does not improve upon the 5-year survival rate when tumor resection is grossly complete. Conversely, the improvement in survival of incompletely excised cases by adjuvant radiotherapy is highly significant. Local tumor control rates show progressive improvement with increasing radiation doses in the range of 800–1500 ret, using the Ellis formula.