INTERSTITIAL RADIOSURGERY IN TREATMENT OF LOW-GRADE GLIOMAS

In this retrospective study the outcome of 324 patients with low-grade gliomas (WHO-Grade II) is evaluated, who from 1979 to 1991 underwent stereotactic biopsy and interstitial radiosurgery (Iodine-125). The patients were selected for interstitial radiosurgery if the tumor was unifocal, well-circumscribed and in diameter less-than-or-equal-to 4 cm. Of these patients 251 had astrocytomas. 29 had oligodendrogliomas, and 44 had oligoastrocytomas. All patients presented with progressive neurological deficit or showed evidence of CT/MRI confirmed tumor growth. The preoperative performance status was greater-than-or-equal-to 70%. Diffusely infiltrative, non-delineated gliomas and gliomas crossing the midline were excluded. Five-year survival rates were 65% for astrocytomas, 80% for oligoastrocytomas and 58% for oligodendrogliomas. In the multivariate analysis age was a significant factor predicting survival. Patients who received temporary implants had a significantly better outcome than those with permanent implants. Radiation toxicity (3.1%) was seen mostly among the permanent implants. No patients required reoperation due to radionecrosis. The findings in this subgroup of gliomas indicate that interstitial radiosurgery using Iodine-125 is effective in controlling tumor growth and is well tolerated. Patients with differentiated and circumscribed gliomas particularly benefit from the treatment.