LONG-TERM PROGNOSIS FOR ATYPICAL AND MALIGNANT MENINGIOMAS - A STUDY OF 71 SURGICAL CASES

To contribute to a better understanding of the prognostic differences between atypical and malignant meningiomas as defined by the World Hea lth Organization (WHO) and the influence of the grade of initial surgi cal excision on postoperative course, 42 cases of atypical and 29 of m alignant meningioma were studied, along with long-term follow up. The two groups were compared with respect to long-term survival, recurrenc e-free survival, and median time to recurrence. The prognostic signifi cance of the Simpson grade of surgical resection and tumor location wa s also considered. Survival at 5 and 10 years was recorded in 95% and 79%, respectively, of patients with atypical meningioma and in 64.3% a nd 34.5% of patients with malignant meningioma (p = 0.001). Recurrence -free survival and median time to recurrence were also significantly l onger in patients with atypical than in those with malignant meningiom as: 11.9 versus 2 years (p = 0.001) and 5 versus 2 years (p < 0.0041), respectively. Six (26%) of the 23 recurring atypical meningiomas beca me malignant. Simpson Grade I resection and location in the cerebral c onvexity, which were closely related, were found to be associated with a significantly better clinical course in the entire series (p less t han or equal to 0.0016). Patients with atypical meningiomas fared bett er than those with malignant meningiomas after incomplete surgical exc ision (Simpson Grades II-III), but the difference was not statisticall y significant. Multivariate analysis using the Cox model indicated tha t radical extirpation (Simpson Grade I vs. II-III) and histological fi ndings (atypical meningioma vs. malignant meningioma) were significant ly related to prolonged survival (p < 0.0003 and p < 0.0388, respectiv ely). In conclusion, the current study shows that for most patients wi th atypical meningioma the prognosis was less severe than for those wi th malignant meningioma, but the risk of a downhill course resulting f rom malignancy after incomplete resection and recurrence was not negli gible (26%). In addition, the WHO classification was found to be inade quate for a minority of the atypical meningioma cases, which currently have the same unfavorable course as cases of malignant meningioma. Th e results also indicate that objective Simpson Grade I extirpation of convexity meningiomas can be successful despite histological findings of malignancy.