Stereotactic Iodine-125 Interstitial Irradiation Of Deep-seated Low-grade Glioma

Objective:. Glioma is the most common malignant tumor. There is no standard therapy for low-grade deep-seated glioma which is not suitable for surgaical resection or cannot be completely resected.. The favorable survial can be achieved for the patient with low-grade glioma. Stereotactic interstitial brachytherapy can deliver a high dose to the tumor volume while sparing surrounding normal tissue. Radiobiological advantages include a lower oxygen enhancemen tratio, reoxygenation and the accumulation of tumor cells in a sensitive phase of the cell cycle during the course of brachytherapy.Brachytherapy treatments for glioma patients were performed with photon radiation of 125I seeds. The seeds were implanted into the tumor under local anesthesia with stereotactic control. The integration of CT with modern stereotactic systems has made it possible to implant radioactive sources into brain tumor targets safely and accurately, CT-controlled interstitial brachytherapy treatments, including image fusion techniques, allow the identification and correction of potential flaws of the operation.This study was undertaken to test the feasibility and the risk of Interstitial Irradiation of the deeped-seated glioma.Methods: All the 13 cases were undertaken CT/MRI-guided stereotactic biopsies. All the procedures were undertaken under local anesthesia with CT or MRI guided stereotactic system. After histological confirmation of a low-grade glioma, stereltactic iodine-125 seed implantation was performed immediately .Clinical and neuroradiological follow-up examination was performed 3 months after Stereotactic Iodine-125 Interstitial Irradiation. In the CT/MRI images , the"triple ring"(tumor necrosis, reactive ring and edema)developing after the interstitial irradiation of the brain tumors was examined. The images with the triple ring were fused with the planning images, and the isodose curves were superimposed on them. The volumes of the three regions were measured.The effect of time on necrosis and the reactive zone was investigated by dividing the patients into two groups in which the volunetric measurement were performed in 6 months or less (6 patients) or more than 12 months (6 patients) after the implantation, respectively. In these two groups, the volumes of necrosis and edema were calculated separately.Results: Of the 13 cases, 4were male and 9 were female. The ratio of male to female was 1:2.25. Age at presentation of GC ranged from 30 years to 54 years (.median, 42.8 years).The investigation was performed an aveage of 11.8months after low-dose-rate 125I interstitial irradiation of 13 inoperable low-grade gliomas. Based on dose-volume histogram analysis, the dose was prescribed in such a way that at least 90% of the tumor volume received the reference dose. The median prescribed dose was 60Gy (range:60Gy). The prescribed dose was 60Gy to the tumor surface and tumor dose and dose rate were not influenced by tumor location and tumor size. Depending on the size and the shape of the tumor, a median of one puncture(1-2)and a median of five seeds(range:2-10)per tumor were used to achieve a conformal of irradiation of the target volume.Conclusions:1.With the help of TPS, a good coverage index can be achieved.2.Long-term control and good-quality of live can be achieved with IRS in patients with low-grade glioma.3.Tumor progression/tumor recurrence can be effectively controled with IRS.4.The image fusion analysis of the volume of tumor necrosis, reactive ring and edema caused by interstitial irradiation and the ircorrelation with the dose distribution provide valuable information for patient follow-up, treatment options, and effects and side effects of radiotherapy.Long-time follow-up studies in large cohorts should definitively be undertaken.