An afterloading procedure using irridium 192 seeds was developed for the control of residual tumors after surgical removal. This technique made possible the delivery of an expected radiation dose to the lesion with minimum dosage to normal brain tissue. So far thistechnique was used for recurrent glioma patients who had already been treated with over 50 Grey (Gy) of radiation to the lesion externally. For implantation in the tumor, a 45 cm closed-ended flexible polyethylene guide tube with an inner diameter of 1.8 mm and outer diameter of 2.2 mm was used. A flexible polyethylene tube with an inner diameter of 0.5 mm and an outer diameter of 1.0 mm, accommodated the radiation source. At surgery for tumor removal, the guide tubes were aligned on a mesh (Oxycel® gauze) and fixed to the tumor bed using silver clips. The external portion of these tubes were anchored to the scalp. Radiation therapy began soon after the patient recovered from surgery. The radiation sources were inserted into the guide tubes and the dose for each patient was determined from the computer outputs of dose distribution calculated from the actual localization of the sources in the tissue. Total dose to the lesion was about 50-66 Gy at a 0.5 cm depth from the surface of the tumor bed.
Four patients were treated with this technique. The first case (malignant astrocytoma) was complicated by the tubes slipping out during therapy, and died 20 months afterwards. The second case (malignant oligodendroglioma) completed this therapy, survived for 20 months, and expired due to metastatic lesions in other portions of the brain. The other two cases were still alive without recurrence over 6 and 7 months after the therapy. The results indicated that this procedure should be considered for the recurrent glioma patient.
