RADT-32. ADJUVANT RADIOTHERAPY VERSUS SURVEILLANCE FOR GRADE 2 INTRACRANIAL MENINGIOMAS: A MULTICENTER STUDY

Abstract

Abstract BACKGROUND To compare the outcomes between adjuvant radiotherapy (ART) and surveillance in patients with grade 2 intracranial meningiomas (MNG2s) after surgical resection.Materials and METHODS This multicenter study included 518 patients with newly diagnosed MNG2 who underwent resection between 1998–2018. Patients receiving ART with conventional fractionation (n = 158) were compared with those undergoing surveillance (n = 360). Progression-free survival (PFS) and progression/recurrence (P/R) rates were evaluated. Propensity score matching was performed to adjust for covariables (n = 43 in each group). RESULTS The median follow-up was 64.9 months. The median ART dose was 60 Gy in 30 fractions. Patients receiving ART had larger tumors (median, 5.0 vs. 4.5 cm, P < 0.001) and less frequent gross total resection (69.6% vs. 85.3%, P < 0.001). In multivariable analysis, ART was associated with significantly improved PFS (HR, 0.34; 95% CI, 0.22–0.53; P< 0.001) and P/R (HR, 0.29; 95% CI, 0.18–0.46; P< 0.001). In the propensity score matched cohort, the 5-year PFS rates were 80.8% vs 57.7% (P = 0.020) in the ART and surveillance group, respectively. Even in patients receiving gross total resection, the 5-year PFS (85.0% vs. 64.7%; HR, 0.50; 95% CI, 0.27–0.91; P = 0.023) and P/R rates (15.2% vs. 32.0%; HR, 0.50; 95% CI, 0.25–0.96; P = 0.038) were significantly improved by ART. Using recursive partitioning analysis in patients undergoing surveillance, we classified patients to low-, intermediate-, or high-risk of P/R based on surgical extent, tumor size, and Ki-67 index. The 5-year P/R rates in the low-, intermediate-, and high-risk groups were 18.6%, 37.9%, and 65.3%, respectively. CONCLUSION ART significantly improved PFS and P/R in MNG2s irrespective of surgical extent and should be recommended after both gross total and partial resection. A recursive partitioning analysis model for P/R may guide clinicians for decision making in resected MNG2s.