Iodine-125 interstitial irradiation for cerebral gliomas

In this retrospective review the outcome of 539 patients is evaluated, who from 1979 through 1991 underwent stereotactic biopsy and interstitial irradiation using iodine-125 implants. Permanent (lost) 125-I implants were used in 345 cases (64%) (1979-1985), temporary (removable) implants in 194 cases (36%) (1985-1991). The patients were selected for interstitial irradiation on the basis of histological classification, location and circumscription of their tumours (106 pilocytic astrocytomas, 251 astrocytomas WHO grade II, 29 oligodendrogliomas, 44 oligo-astrocytomas, 75 anaplastic astrocytomas and 34 glioblastomas). Diffusely infiltrative non-delineated gliomas and gliomas crossing the midline were excluded. Five-year survival rates were 77% for pilocytic astrocytomas, 65% for astrocytomas WHO II, 80% for oligo-astrocytomas, and 58% for oligodendrogliomas. The 2-year survival rates were 36% for anaplastic gliomas and 16% for glioblastomas. Operative morbidity due to stereotactic biopsy, implantation, and explantation of seeds was 3.9%. In the subgroups of patients with astrocytomas (WHO-II), pilocytic astrocytomas and malignant gliomas age was a significant factor predicting survival. Patients with astrocytomas WHO II who received temporary implants had a significantly better outcome than those with permanent implants. Radiation toxicity (3.1%) was seen mostly among the permanent (lost) implants. No patients required re-operation due to radionecrosis. The findings among this subgroup of gliomas indicate that interstitial implant irradiation using 125-I is effective in controlling tumour growth and is well tolerated. Patients with differentiated and circumscribed gliomas particularly benefit from the treatment.