MNGI-10. ATYPICAL MENINGIOMA: EARLY OUTCOMES WITH OR WITHOUT POSTOPERATIVE RADIATION

Abstract

Abstract BACKGROUND Adjuvant radiotherapy (RT) in atypical meningioma, especially for gross-totally resected tumors, remains controversial. METHODS We retrospectively identified histologically-confirmed cases of WHO Grade II atypical meningioma at a large academic institution from 2004–2018. Clinicodemographic, surgical, radiation therapy (RT), and histopathologic data were collected, as well as imaging and clinical outcomes, with a median follow-up time of 26 months (IQR 32). Patients were stratified by resection status and whether or not upfront RT was administered. Additionally, subanalyses were performed to compare external beam RT (EBRT) and stereotactic radiosurgery (SRS). Progression was defined by radiology report. RESULTS Of 122 patients, 45 were excluded for lacking adequate records of previous treatment, less than 3 months follow-up, or lacking MR imaging. Of 77 patients analyzed, 57% (44/77) were female; median 59-years-old. 48% (24/50) of gross-total-resections (GTR) received upfront RT – only a single case progressed, at 39 months. Of 26 GTR patients without upfront RT, 8/26 (31%) progressed at median 19.5 months – of these, 2 were lost to follow-up, 5 received salvage RT, and 1 had surgery alone. Adjuvant RT was associated with superior progression free survival (PFS) in GTR (Cox proportional hazard ratio 0.15, likelihood-ratio p=0.025; median PFS not reached). Of 15 subtotal resections (STR) receiving upfront RT, 11 received EBRT and 4 received SRS – 6 progressed (median 37 months), all after EBRT. Upfront SRS demonstrated superior PFS over EBRT following STR (p=0.036). Across the cohort there was one confirmed death, a GTR patient (without RT) who suffered an ischemic stroke at 11 months. CONCLUSION This large single-center retrospective analysis indicates adjuvant RT improves PFS in GTR atypical meningiomas, in concordance with prior studies. It is limited by short median follow-up, possibly related to long-term stability in treated patients. In STR tumors, SRS may contribute to improved PFS compared to EBRT.