Dose–response relationship in patients with newly diagnosed atypical meningioma treated with adjuvant radiotherapy

Purpose: This study aimed to identify the radiation dose–response relationship in patients with newly diagnosed atypical meningioma (AM) treated with adjuvant radiotherapy (ART) using conventional fractionation. Methods: In total, 158 patients who underwent surgery and ART between 1998 and 2018 were reviewed. Among these patients, 135 with complete information on radiotherapy (RT) dose/fractionation and pathological reports were analyzed. We entered RT dose as a continuous variable into the Cox regression model using penalized spline to allow for a nonlinear relationship between RT dose and events. Local control (LC), progression-free survival (PFS), and overall survival (OS) were evaluated. The corresponding biological equivalent dose in 2 Gy fractions (EQD2) was calculated using an α/β ratio of 4 Gy. Results: The median follow-up duration was 56.0 months. The median ART dose delivered was 61.2 Gy in 24–34 daily fractions, corresponding to a median EQD2 of 59.16 Gy. In multivariate analysis, larger size and higher mitotic count were associated with significantly reduced LC (P < 0.001 and P = 0.002, respectively), PFS (P < 0.001 and P = 0.006, respectively), and OS (P = 0.006 and P = 0.001, respectively). Meanwhile, a higher RT dose was significantly associated with improved LC, PFS, and OS. Moreover, RT showed a dose-dependent effect on LC, PFS, and OS; local failure, tumor progression, and death were reduced by 12%, 12%, and 16%, respectively, per 1 Gy increase in the dose (EQD2). Conclusion: The dose of ART in AM has a dose–response relationship with LC and survival outcomes.