Ｌｏｗ‐ｇｒａｄｅ　ｇｌｉｏｍａの放射線治療成績　　予後因子と有害事象の検討

Purpose: To evaluate the results of radiotherapy for low-grade gliomas focusing on the factors influencing progression-free rate, survival, and late complications.<BR>Materials and Methods: Forty-two patients consisting of 24 grade II astrocytomas and 18 oligoastrocytomas were treated with radiotherapy at Niigata University Hospital between 1982 and 1997. The patients ranged in age from 3 to 75 years (median: 39 years), of whom 8 were ≤15 years old. Twenty-six patients underwent tumor removal and 22 received chemotherapy mainly combined with radiotherapy. Radiotherapy was delivered in 2-Gy fractions to the tumor bed defined by CT or MRI usually with a 2-cm margin for a total dose ranging between 44 and 66 Gy (median: 50 Gy). Median follow-up time was 74.5 months (range: 4-193 months), and the progression-free rate and survival were calculated using the Kaplan-Meier method. Variables examined for prognostic significance included patient's age, gender, Karnofsky performance status (KPS), tumor location, pathology, maximum tumor diameter, calcification, enhancement with contrast material on CT or MRI, extent of tumor resection, radiation parameters (total dose and safety margin), interruption of radiotherapy, and chemotherapy. A log-rank test was used to analyze the statistical significance of differences in factors.<BR>Results: Tumor recurrence occurred in 10 adult patients. The 5-and the 10-year progression-free rates were 73% and 67% respectively. Seven were in-field recurrence, two were marginal, and one was a new lesion in the opposite cerebral hemisphere isolated from the original tumor. Nineteen patients had died at the time of the last follow-up and seven died of tumor progression. The overall survival at 5 and 10 years were 80% and 48% respectively. The cause-specific survival at 5 and 10 years were 92% and 73% respectively. Our analysis revealed that patient's age, extent of tumor resection, safety margin, and maximum tumor diameter were the significant factors influencing the progression-free rate. The factors influencing overall survival were age, maximum tumor diameter, and KPS. Age and extent of tumor resection were significant factors in causespecific survival. Deterioration of quality of life occurred in 9 adult patients mainly due to dementia after radiotherapy. Most of them had the large frontal tumor and received chemotherapy.<BR>Conclusions: Radiotherapy was effective in the treatment of low-grade gliomas. An effort to reduce complications is required, because 9 of 34 adult patients suffered from dementia after radiotherapy in this study. The management of low-grade gliomas in adult patients is still controversial. Standardization of treatment strategy considering prognostic factors is awaited.