CTNI-55. PREDICTIVE FACTORS FOR HIGH GRADE TRANSFORMATION IN BENIGN MENINGIOMAS

Abstract OBJECT Meningiomas are generally slow-growing, benign tumors, most of which are classified as WHO Grade I. Rarely, benign meningiomas may recur after surgery with transformation into WHO Grade II atypical meningiomas. As atypical meningiomas are different from benign meningiomas in terms of clinical course, and prognosis, predicting the transformation is important for patient management. The purpose of the study was to investigate the radiological and pathological factors that predict the risk of tumor progression from benign to atypical meningioma. METHOD All patients treated with recurrent meningiomas in whom the tumor showed histopathologically confirmed high grade transformation between 2001 and 2017 were included. To evaluate the predictors for transformation, patients’ medical records for previous benign meningioma before transformation were collected. Each patient was matched with 4 age and sex-matched controls treated with benign meningioma, and were analyzed. RESULTS Fourteen patients with high grade transformation were included. The median time interval of transformation was 63 months (range of 19 – 132). Multivariate analysis indicated that increased mitotic index (OR, 10.409, 95% CI, 1.297–83.549, p=0.027) was significant predictive factor of transformation. And prominent peritumoral edema (OR, 33.822, 95% CI, 0.935–223.688, p=0.054) showed relative risk for transformation. CONCLUSION Increased mitotic index and prominent peritumoral edema may be predictors for high grade transformation of benign meningiomas. Although these tumors do not meet the criteria for atypical meningioma, they may be required more attentive observation and management than other benign meningiomas.