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NCOG-49. COMBINED NECROSIS AND BRAIN INVASION PREDICT RADIO-RESISTANCE AND TUMOR RECURRENCE IN ATYPICAL MENINGIOMA


 
 
 Meningiomas are the most common tumors in the central nervous system, with variable recurrence rates depending on WHO grading. Atypical (WHO grade II) meningioma has a higher recurrence rate than benign meningioma (WHO grade I). The efficacy of adjuvant radiotherapy (RT) to improve tumor control has been questioned.
 
 
 
 This cohort study retrospectively reviewed all patients at St. Michaels Hospital Tumor Patient Database with a diagnosis of atypical meningioma (AM) who underwent surgical resection between 1995 and 2015. Patient and tumor characteristics such as location, neuropathological diagnosis, resection extent, RT and time to reoccurrence or progression were recorded. Resection extent was defined by Simpson Grading Scale as either Gross Total (GTR) or Subtotal (STR) resection. Cox univariate regression and Kaplan-Meier survival analysis were employed to identify risk factors for recurrence and radio-resistance.
 
 
 
 In our cohort of 181 patients, the combination of necrosis and brain invasion was associated with an increased reoccurrence risk (HR= 4.560, P=0.001) and the lowest progression-free survival relative to other histopathological predictors. This trend was maintained after GTR (P=0.001), whereas necrosis alone and combined necrosis and brain invasion were both associated with low progression-free survival in STR (P=0.001). Radiotherapy was associated with decreased progression-free survival (P=0.001), especially in patients who received GTR (P=0.001). This trend was maintained in patients with necrosis alone (P=0.002) but especially in patients with combined necrosis and brain invasion (P=0.001).
 
 
 
 Combined necrosis and brain invasion is a strong predictor of tumor recurrence and radio-resistance in AM, regardless of extent of resection or RT.
