Long-term prognosis for atypical and malignant meningiomas: a study of 71 surgical cases

Abstract

<jats:p>To contribute to a better understanding of the prognostic differences between atypical and malignant meningiomas as defined by the World Health Organization (WHO) and the influence of the grade of initial surgical excision on postoperative course, 42 cases of atypical and 29 of malignant meningioma were studied, along with long-term follow up. The two groups were compared with respect to long-term survival, recurrence-free survival, and median time to recurrence. The prognostic significance of the Simpson grade of surgical resection and tumor location was also considered. Survival at 5 and 10 years was recorded in 95% and 79%, respectively, of patients with atypical meningioma and in 64.3% and 34.5% of patients with malignant meningioma (p = 0.001). Recurrence-free survival and median time to recurrence were also significantly longer in patients with atypical than in those with malignant meningiomas: 11.9 versus 2 years (p = 0.001) and 5 versus 2 years (p &lt; 0.0041), respectively. Six (26%) of the 23 recurring atypical meningiomas became malignant. Simpson Grade I resection and location in the cerebral convexity, which were closely related, were found to be associated with a significantly better clinical course in the entire series (p ¾ 0.0016). Patients with atypical meningiomas fared better than those with malignant meningiomas after incomplete surgical excision (Simpson Grades II-III), but the difference was not statistically significant. Multivariate analysis using the Cox model indicated that radical extirpation (Simpson Grade I vs. II-III) and histological findings (atypical meningioma vs. malignant meningioma) were significantly related to prolonged survival (p &lt; 0.0003 and p &lt; 0.0388, respectively). In conclusion, the current study shows that for most patients with atypical meningioma the prognosis was less severe than for those with malignant meningioma, but the risk of a downhill course resulting from malignancy after incomplete resection and recurrence was not negligible (26%). In addition, the WHO classification was found to be inadequate for a minority of the atypical meningioma cases, which currently have the same unfavorable course as cases of malignant meningioma. The results also indicate that objective Simpson Grade I extirpation of convexity meningiomas can be successful despite histological findings of malignancy.</jats:p>

Clinicopathologic Features of Aggressive Meningioma Emphasizing the Role of Radiotherapy in Treatment

“…This suggests that the endocrinological influences important in the genesis of benign meningiomas are not active in aggressive variants [15,20,27,29,30,38,40]. Regarding the tumor location, only five cases (31.25%) were basal meningiomas, while the majority of cases were convexity and parasagittal tumors as reported in most series of aggressive meningioma [6,10,27,30,40]. The average age at the time of presentation was 54.1 years.…”

“…Recurrence-free survival even after complete removal has been reported to be highly dependent on histological grade and to be significantly different between atypical and anaplastic tumors [2,21,28,30,34]. Although the 5-year recurrence rate after total removal is only 3-4% for benign meningiomas, it rises to 35-38% with atypical and 78-84% with anaplastic meningiomas [14,23,27]. 38.5% of our patients originally diagnosed as having atypical meningioma experienced recurrence in spite of total surgical resection within a relatively short period.…”

“…The mitotic index was the cornerstone for grading but other criteria suggesting aggressive behavior were not neglected. The different criteria used to define different grades make it troublesome to compare the data from different studies [7,20,22,27,28,30,40]. Counting mitotic figures is a simple, reliable, and low-cost procedure that requires no additional preparation.…”

“…Both types carry a higher rate of recurrence in comparison with grade I meningiomas. However, the clinical behavior of atypical meningiomas is considered intermediate between the common benign meningiomas and the worse anaplastic meningiomas [4,20,22,27].…”

“…Radical surgical excision of meningiomas has always been correlated with better prognosis [27,33,40]. The use of adjuvant radiotherapy in the treatment of aggressive meningiomas is still controversial.…”