Article
Brain invasion in meningiomas previously classified as WHO grade I has limited impact on outcome
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Published: | June 18, 2018 |
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Objective: For meningiomas the 2016 revision of the WHO classification of tumors of the central nervous system introduced brain invasion per se as a sufficient condition to classify as grade II. We analyzed whether meningiomas previously graded as WHO grade I differ in prognosis according to the feature of brain invasion.
Methods: All consecutive patients having been operated between 1/2009 and 03/2016 upon a meningioma being diagnosed as WHO grade I according to the previous (2007) WHO classification system were included. The reference point of the study was the date of surgery. Date of last follow up was 11/2017. Study endpoint was the date of tumor progression. Prognostic factors were obtained from multivariate proportional hazards models.
Results: 788 adult patients were included. The median follow-up was 43 months (range: 3-78 months). Gross total resection (GTR) was achieved in 594 (75.4%) patients, adjuvant radiotherapy was applied in 71 (9%) patients. Brain invasion was diagnosed by histology in 21 (2.7%) patients. Patients with/without brain invasion did not differ in terms of age and extent of resection. Patients with histologically proven brain invasion received more often adjuvant radiotherapy (8.5% vs 28.6%, p=0.008). 80 patients experienced tumor recurrence/ progression, overall survival was not reached in the majority of patients. The overall median PFS for patients with (without) brain invasion was 22 (23) months (p=0.48). Outcome of meningiomas with/without brain invasion after surgery alone was similar (p=0.96). In univariate and multivariate models complete resection gained favorable prognostic influence for PFS (p<0.001). Brain invasion and radiotherapy were not associated with PFS.
Conclusion: Among meningiomas classified as grade I according to the WHO 2007 grading system histological proven brain invasion is a rare event. Extent of resection was the most powerful prognostic factor. The sole factor of brain invasion seems to be of limited impact for prognosis and may notper se justify the application of adjuvant radiotherapy.