Malignant Transformation of Hemispheric Low-Grade Gliomas: Clinical Analysis and Prognostic Factors

ABSTRACT

INTRODUCTION: It has been reported that the survival of low-grade glioma patients depends upon the time of malignant transformation. The authors presents the clinical analysis of histologically proven trasformed gliomas. MATERIALS AND METHODS: A total 92 patients who were consecutively treated and histologically confirmed hemispheric low-grade gliomas between 1980 and 1998 were analyzed and followed. All cases meet the criteria of WHO glioma classification of grade II. RESULTS: The mean follow-up period was 73 months. Twenty two among 92 cases(24%) were histologically proven to be transformed into malignant ones. The mean time to transformation was 56 months. The 5-year and 10-year survival rates of the transformed group were 66% and 30% respectively and significantly different from the survival rates of the non-transformed group(p=0.0018). Among clinical factors at presentation, the initial tumor volume had a tendency to be larger in the transformed group than that of the non-transformed group and became significant when it was divided into more than 30cm3 or not(p=0.02). Among therapeutic factors, the extent of removal had no influence on the rate of malignant transformation. But postoperative radiation therapy were more frequently given to the pre-transformed group than the non-transformed group and the frequency was significantly different(p=0.02). CONCLUSIONS: The authors had found that the initial tumor volume and radiation therapy could be clinical prognostic factors for the malignant transformation of low-grade gliomas.