NCOG-54. Timing of adjuvant radiotherapy impacts overall survival for atypical intracranial meningiomas: a National Cancer Database (NCDB) analysis

INTRODUCTION Atypical intracranial meningiomas are characterized by brain invasion and faster growth than lower grade counterparts. Adjuvant radiotherapy (aRT) improves survival for patients with atypical meningiomas (AMs). This study assesses the association between timing of initiating radiotherapy following surgery upon survival. METHODS Patients >18 years old with intracranial AMs surgically resected (2004-2019) within the National Cancer Database were included. Kaplan-Meier survival curves for each variable were generated. Cox proportional hazards models were developed to assess the association between timing of initiating radiotherapy with overall survival, while controlling for age, sex, race, ethnicity, facility type, tumor size, comorbidities, resection type, and systemic therapy. RESULTS 5,452 patients were included; 28.28% received aRT. Median time to initiation of radiation post-surgery was 9 weeks. On multivariate analysis, starting radiotherapy within 6 weeks post-surgery (HR 0.73, p<0.01), between 6-12 weeks (HR 0.73, p<0.01), and between 12 weeks-6 months (HR 0.69, p<0.01) all showed survival benefits compared to not receiving radiotherapy, whereas initiating radiotherapy >6 months post-surgery did not offer survival benefits (HR 0.49, p=0.22). Pairwise Wald tests showed no significant differences among the <6 weeks, 6–12 weeks, and 12 weeks–6 months groups (p=0.97, 0.78, 0.71). On subgroup analysis, following gross total resection, initiating radiotherapy <6 weeks (HR 0.53, p=0.01) or between 6-12 weeks (HR 0.59, p<0.01) offered survival benefits, whereas initiating radiotherapy later did not. Following subtotal resection, initiating radiotherapy between 12 weeks-6 months (HR 0.60, p=0.01) offered survival benefits whereas initiating radiotherapy earlier or later did not. CONCLUSION For AMs, radiotherapy is associated with improved survival if initiated <6 months post-surgery. Starting radiotherapy <12 weeks after surgery is associated with improved survival following gross total resection and initiating radiotherapy between 12 weeks-6 months is associated with improved survival following subtotal resection. We recommend early aRT following gross total resection for atypical meningiomas.