Brachytherapy - Results of two different therapy strategies for patients with primary glioblastoma multiforme

BACKGROUND. In the current study, the authors describe and compare two diff erent strategies of brachytherapy for the treatment of patients with primar y glioblastoma multiforme (GBM). METHODS. The study was comprised of 84 patients. Forty-five patients were i mplanted with permanent or temporary low activity iodine-125 (I-125) seeds in Cologne and 21 patients were implanted with temporary iridium-192 (Ir-19 2) wires in Amsterdam. Both groups received external beam radiation therapy (EBRT); the I-125 group received 10-30 grays (Gy) with the implant in situ and the Ir-192 group received 60 Gy before implantation. In Cologne, impla ntation was performed after a diagnostic stereotactic biopsy whereas in Ams terdam implantation took place after cytoreductive diagnostic surgery. In a ddition, 18 patients in Amsterdam served as a control group. This group rec eived only EBRT after cytoreductive surgery. RESULTS. In both groups the mean age of the patients was between 50-55 year s, with 80% of the patients age > 45 years. The mean implantation volume en compassed by the referenced isodose was 23 cm(3) for I-125 and 48 cm(3) for Ir-192. Initial dose rates were 2.5-2.9 centigrays (cGy)/hour for permanen t I-125, 4.6 cGy/hour for temporary I-125, and 44-100 cGy/hour (mean, 61 cG y) for Ir-192. A total dose of 50-60 Gy, 60-80 Gy, and 40 Gy, respectively, was administered at the outer margins of the tumor. The median survival wa s approximately 16 months for both the I-125 group and the Ir-192 group. Th is was 6 months longer than the median survival in the control group. Reope rations were performed in 4 patients in the I-125 group (9%) versus 7 patie nts in the Ir-192 group (33%). No complications or late reactions were repo rted in the I-125 group, whereas one case of hemorrhage and three cases of delayed stroke were observed in the Ir-192 group. CONCLUSIONS. The equal median survival times in these two brachytherapy gro ups with such different dose rate radiation schedules support the hypothesi s that dose rate does not play a major role in the survival of patients wit h primary GEM. (C) 2000 American Cancer Society.