Histopathological features predictive of local control of atypical meningioma after surgery and adjuvant radiotherapy

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OBJECTIVE

The goal of this study was to investigate the impact of adjuvant radiotherapy (RT) on local recurrence and overall survival in patients undergoing primary resection of atypical meningioma, and to identify predictive factors to inform patient selection for adjuvant RT.

METHODS

One hundred eighty-two patients who underwent primary resection of atypical meningioma at a single institution between 1993 and 2014 were retrospectively identified. Patient, meningioma, and treatment data were extracted from the medical record and compared using the Kaplan-Meier method, log-rank tests, multivariate analysis (MVA) Cox proportional hazards models with relative risk (RR), and recursive partitioning analysis.

RESULTS

The median patient age and imaging follow-up were 57 years (interquartile range [IQR] 45–67 years) and 4.4 years (IQR 1.8–7.5 years), respectively. Gross-total resection (GTR) was achieved in 114 cases (63%), and 42 patients (23%) received adjuvant RT. On MVA, prognostic factors for death from any cause included GTR (RR 0.4, 95% CI 0.1–0.9, p = 0.02) and MIB1 labeling index (LI) ≤ 7% (RR 0.4, 95% CI 0.1–0.9, p = 0.04). Prognostic factors on MVA for local progression included GTR (RR 0.2, 95% CI 0.1–0.5, p = 0.002), adjuvant RT (RR 0.2, 95% CI 0.1–0.4, p < 0.001), MIB1 LI ≤ 7% (RR 0.2, 95% CI 0.1–0.5, p < 0.001), and a remote history of prior cranial RT (RR 5.7, 95% CI 1.3–18.8, p = 0.03). After GTR, adjuvant RT (0 of 10 meningiomas recurred, p = 0.01) and MIB1 LI ≤ 7% (RR 0.1, 95% CI 0.003–0.3, p < 0.001) were predictive for local progression on MVA. After GTR, 2.2% of meningiomas with MIB1 LI ≤ 7% recurred (1 of 45), compared with 38% with MIB1 LI > 7% (13 of 34; p < 0.001). Recursive partitioning analysis confirmed the existence of a cohort of patients at high risk of local progression after GTR without adjuvant RT, with MIB1 LI > 7%, and evidence of brain or bone invasion. After subtotal resection, adjuvant RT (RR 0.2, 95% CI 0.04–0.7, p = 0.009) and ≤ 5 mitoses per 10 hpf (RR 0.1, 95% CI 0.03–0.4, p = 0.002) were predictive on MVA for local progression.

CONCLUSIONS

Adjuvant RT improves local control of atypical meningioma irrespective of extent of resection. Although independent validation is required, the authors’ results suggest that MIB1 LI, the number of mitoses per 10 hpf, and brain or bone invasion may be useful guides to the selection of patients who are most likely to benefit from adjuvant RT after resection of atypical meningioma.

ABBREVIATIONS EBRT = external beam radiotherapy; EORTC = European Organization for Research and Treatment of Cancer; GTR = gross-total resection; IQR = interquartile range; KPS = Karnofsky Performance Scale; LFFR = local freedom from recurrence; LI = labeling index; MVA = multivariate analysis; OS = overall survival; RPA = recursive partitioning analysis; RT = radiotherapy; RTOG = Radiation Therapy Oncology Group; SRS = stereotactic radiosurgery; STR = subtotal resection.

Article Information

Correspondence David R. Raleigh: University of California, San Francisco, CA. david.raleigh@ucsf.edu.

INCLUDE WHEN CITING Published online April 6, 2018; DOI: 10.3171/2017.9.JNS171609.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

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Figures

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    Schematic showing study design.

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    Graphs showing outcomes of atypical meningioma according to extent of resection. A: The LFFR according to extent of resection. A GTR (blue) was associated with improved local control by log-rank test (p = 0.03) and MVA (RR 0.2, 95% CI 0.1–0.5, p = 0.002). B: The OS by extent of resection. A GTR (blue) was associated with improved OS by log-rank test (p = 0.02) and MVA (RR 0.4, 95% CI 0.1–0.9, p = 0.02). Figure is available in color online only.

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    Graphs showing outcomes of atypical meningioma according to adjuvant RT. A: The LFFR after GTR, stratified by adjuvant RT. There was a trend toward improved LFFR with GTR+RT by log-rank test (p = 0.10) that was significant on MVA (p = 0.01). B: The OS after GTR, stratified by adjuvant RT. There was no significant difference between groups (p = 0.61, log-rank test). C: The LFFR after STR, stratified by adjuvant RT. Adjuvant RT was associated with improved LFFR by log-rank test (p = 0.01) and MVA (RR 0.2, 95% CI 0.04–0.7, p = 0.009). D: The OS after STR, stratified by adjuvant RT. There was no significant difference between groups (p = 0.63, log-rank test). Figure is available in color online only.

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    Schematic showing RPA for atypical meningioma status post-GTR. Optimal number of splits (3) was based on R2 as calculated by k-fold cross-validation (k = 5).

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