Radiation-therapy of malignant gliomas

On the surgery of glioblastoma multiforme, most cases are beyond the scope for desirable removal of tumors. The restriction of the surgical treatment has inevitably required postoperative radiation therapy. Although patients treated with postoperative radiation therapy showed significantly extended survival rates as compared to those receiving surgical resection alone, the glioblastoma recurred within a 2cm margin of the primary site in more than 90% of the patients and conventional external radiation therapy with a doses of 50-60 Gy did not result in local cure. However, it was reported that survivals extended in proportion to target absorbed doses and suggested that a higher localized radiation dose would improve the poor prognosis of these tumors. In order to obtain a local cure of glioblastoma, the first step of therapy should be an intensive local treatment. Intraoperative radiation therapy (IOR) and brachytherapy using high activity iodine-125 or iridium-192 become a logical local treatment for sterilizing the remaining malignant remnants by a high target absorbed dose without damaging surrounding brain tissues. IOR for 19 patients with glioblastoma resulted in a 2-year survival rate of 61.4%. Brachytherapy has shown excellent local effects for recurrent tumors.