PERMANENT I-125 BRAIN-STEM IMPLANTS IN CHILDREN

Between 1988 and 1997, 28 children have had iodine-125 implants for CN S tumors performed in our institution. Ten had stereotactic implantati on in the brain stem region, and nine had the diagnosis of brain stem glioma (8 diffuse pontine, 1 midbrain tumor). Their ages ranged from 1 .8 to 12 years. All patients had histological confirmation of malignan cy (7 high-grade glioma, 2 low-grade glioma, 1 PNET). Diffuse pontine glioma patients received external beam radiation (50 Gy) followed by a fractionated stereotactic boost of 3 Gyx4 fractions. After 4-6 weeks, patients were reevaluated for stereotactic interstitial I-125 therapy . The planned implant dose was 82.9 Gy to the enhancing tumor (4 cGy p er h). Preliminary results indicated that no surgical complications we re associated with the catheter placement. Four patients have died (7- 9 months from diagnosis) and four patients remain alive (5-38 months f rom diagnosis, median 10 months). Two autopsies confirmed the presence of progressive glioblastoma multiforme and intralesional necrosis. In one patient who received an implant alone for midbrain LGA, necrosis without tumor was found on biopsy after 36 months. He was successfully treated with hyperbaric oxygen therapy. The implementation of permane nt I-125 implants appears to have a role in the management of pediatri c CNS malignancy. This study confirms the results of previous reports regarding the safety of stereotactic interstitial brachytherapy in the blain stem. Tumor control for patients with high-grade brain stem gli oma remains poor even with high focal radiation doses.