Outcome and patterns of failure following limited-volume irradiation for malignant astrocytomas

Between January 1982 and June 1986, 60 consecutive patients with high-grade astrocytomas [39 glioblastoma multiforme (GBM), 21 anaplastic astrocytoma (AA)] were treated with radiation therapy after biopsy (13 patients) or resection (47 patients). Fifty-three patients were treated with limited-volume irradiation, and seven patients received whole-brain irradiation. The mean tumor dose was 65.4 Gy. In 35 patients, chemotherapy was given as part of their initial treatment. The 1- and 2-year survivals for GBM patients were 40 and 14%, respectively. Survival figures for AA patients were 76 and 52% at 1 and 2 years, respectively. The progression-free rate at 1 year was 13% in GBM and 29% in AA patients. Thirty-four of 48 patients who received limited-volume irradiation had evidence of progression on postirradiation CT scans. Six patients (3 GBM, 3 AA) had evidence of a new intracranial metastatic site on CT scan. In three patients the metastasis was within the previously irradiated volume, and in the other three patients, it was outside this volume. All six had evidence of progression of their primary tumor at the original location on CT scan prior to the discovery of the metastatic site. Twenty-one patients (15 GBM, 6 AA) had at least one postirradiation reoperation for a recurrent mass. Nineteen patients had recurrent tumors in the primary site, and two patients had necrosis but no tumor. Patients who received limited-volume irradiation for high-grade astrocytomas achieved the same survival results as patients treated previously with whole brain irradiation. New intracranial metastases did not influence the outcome, since these were always antedated by tumor progression at the primary site.