PERMANENT I-125 IMPLANT AND EXTERNAL BEAM RADIATION-THERAPY FOR THE TREATMENT OF MALIGNANT BRAIN-TUMORS

Survival data of 114 patients treated for malignant brain tumors with I-125 interstitial radiation therapy at Henry Ford Hospital, Detroit, Mich. (1986-1990), are presented. The first 64 patients were treated with temporary I-125 implants with a total prescribed dose of 60 Gy at a dose rate of 40 cGy/h. In order to reduce the risk of injury to the surrounding normal tissue associated with high-dose brachytherapy, a new approach was initiated using permanent implants with a lower dose rate; 50 patients were treated after surgical resection with permanent implantation of I-125 seeds at a lower dose rate of 4-7 cGy/h, with a total dose of 10,000-12,000 cGy, and concurrent external radiation therapy of 5,000 cGy. The rationale of this protocol was to increase the effectiveness of the low-dose-rate implant by a concurrent 'daily' boost of external radiation, thus inhibiting the proliferation of tumor cells during the protracted low-dose radiation treatment. Survival was compared between groups with permanent and temporary implants in terms of effectiveness in tumor control as well as impact on clinical condition. Low-dose-rate implant with concurrent external radiation therapy seems to offer the best chance for long-term survival without deterioration in the clinical condition.