The results of radiation therapy for intracranial meningiomas. With special reference to the natural course of the tumor size after radiotherapy

Twenty-four cases with intracranial meningioma received radiation therapy from 1967 to 1995 at Tenri Hospital. Two received preoperative radiotherapy and 22 post operative radiotherapy. Of all, 11 were benign, 9 were malignant and 4 were reported only as meningioma. The extent of surgery consisted of total resection in 4, subtotal resection in 10, partial resection in 6, biopsy in 2, exploration in 1 and unknown in 1. Twelve were initial treatments and another 12 were salvage treatments. In all cases, radiation therapy was given a mean dose of 53.6 Gy with 6 or 10 MV X-rays using conventional fractionation. The mean follow-up interval is 56.7 months. Total cause specific survival at 5 and 10 years were 79% and 69%, respectively. The 10-year recurrence-free survival was 100% in benign and 61% in malignant meningiomas. The clinical course of benign meningiomas suggested the value of postoperative radiation therapy, but that of malignant meningiomas were divided into 2 groups, in which some one had recurrence just after completion of radiotherapy or another had local control. It seemed that there were some radio-resistant varieties in malignant meningiomas. The result of the consecutive follow-up by enhanced CT or MRI revealed benign meningiomas had a tendency to decrease in size in a long interval and some malignant meningiomas changed their size soon after radiotherapy. From analysis of our study we conclude that radiation therapy is a useful post-surgical treatment for intracranial meningiomas. (author)