RADT-20. POSTOPERATIVE RADIOTHERAPY PROVIDES ADDITIVE PROGRESSION-FREE SURVIVAL BENEFIT IN ATYPICAL MENINGIOMAS REGARDLESS OF EXTENT OF RESECTION

Abstract WHO Grade II meningiomas represent a minority of all meningiomas. The creation of treatment algorithms has remained challenging, with the need to add postoperative radiotherapy (RT) following satisfactory gross total resection being oftentimes debated. Thus, the goal of this study was to understand which factors, if any, predispose to recurrence of atypical meningiomas following resection. Therefore, we retrospectively review a 90-patient cohort of WHO grade II meningiomas who underwent surgical resection. Patients were clustered based on tumor location, (convexity or non-convexity) and whether they had received postoperative RT. Following extraction of biographic characteristics, the extent of tumor resection and tumor recurrence were measured. A detailed uni- and multivariate analysis was carried out to determine which factors, if any, predisposed to recurrence. The cohort consisted of 90 patients with a WHO Grade II meningiomas. A gross total resection was achieved in 66.7% of patients. Patients who had a gross total resection and received postoperative RT had longer progression-free survival (p = 0.031) than patients with subtotal resections (STR), regardless of radiation status, and patients with a GTR who did not receive radiation. On uni- and multivariate analysis, receiving postoperative RT was the only factor associated with no recurrence of disease (p = 0.023); no association was found for extent of resection (p = 0.63) or location (p = 0.18). In conclusion, the treatment of WHO grade II meningiomas remains challenging. In this study, we showed how the addition of radiotherapy remains beneficial even in cases of gross total resection, regardless of location. We postulate how microscopic disease not observed on MRI may be responsible for these findings.