Abstract
PURPOSE/OBJECTIVE(S)
Conventionally fractionated radiotherapy (RT) is a defined treatment following surgery for atypical and malignant meningioma. However, the optimal radiotherapeutic approach is not well defined. We present the results of our dose-escalation strategy.
MATERIALS/METHODS
Consecutive patients with a histopathologic grade 2 or 3 meningioma treated with RT were retrospectively reviewed. The primary outcome was progression-free survival (PFS), and secondary outcomes included cause-specific survival (CSS), overall survival (OS), local failure and incidence of radiation necrosis. We specifically compared the dose-escalation cohort, defined as those treated with ≥66 Gy EQD2 (equivalent dose in 2 Gy fractions, a/b = 10), to the standard dose cohort receiving <66 Gy EQD2. We defined adjuvant as RT delivered within 6 months of surgery otherwise the treatment was salvage.
RESULTS
A total of 118 patients with Grade 2 (111/118) or 3 (7/118) meningioma were identified. 54/118 (45.8%) received dose-escalation and 64/118 (54.2%) standard dosing. 34/54 (63.0%) dose-escalated and 45/64 (70.3%) standardly dosed were treated adjuvantly. The median follow-up was 45.4 months (IQR: 24.0-80.0 months) and median OS was 9.7 years. Post-operative residual disease was present in all dose-escalated patients, as compared to 65.6% in the standard dose cohort. PFS at 3-, 4- and 5-years in the dose-escalated vs. standard dose cohort were 78.9%, 72.2% and 64.6% vs. 57.2%, 49.1% and 40.8%, respectively, (p = 0.030). On multivariable (MVA) analysis, dose-escalation (HR: 0.544, 95% CI: 0.303-0.977, p = 0.042) was associated with improved PFS, whereas ≥2 surgeries (HR: 1.989, 95% CI: 1.049-3.773, p = 0.035) and older age (HR: 1.035, 95% CI:1.015-1.056, p<0.001) associated with worse PFS. The cumulative risk of local failure at 3-, 4- and 5-years in the dose-escalated vs. standard dose cohort were 16.9%, 23.8% and 31.8% vs. 39.6%, 45.6% and 53.9%, respectively, favoring dose-escalation (p = 0.016). MVA confirmed dose-escalation as predictive of a lower risk of LF (HR: 0.483, 95% CI: 0.263-0.887, p = 0.019), while ≥2 surgeries prior to RT predicted for greater LF rates (HR:2.145, 95% CI:1.220-3.771, p = 0.008). A trend was observed for prolonged CSS and OS in the dose escalation cohort (p = <0.1). Seven patients (5.9%) developed symptomatic radiation necrosis (RN) with no significant difference between the two cohorts.
CONCLUSION
Dose-escalated radiotherapy for high grade meningioma to at least 66 Gy is associated with significantly improved rates of local control and PFS with an acceptable risk of RN.
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