JS05.5.A INCIDENTAL MENINGIOMA: RESULTS FROM THE IMPACT INTERNATIONAL MULTICENTRE STUDY
Authors: A I Islim, C P Millward, R J Piper, D M Fountain, S Mehta, R Kolamunnage-Dona, U Ali, S D Koszdin, T Georgious, S J Mills, A R Brodbelt, R K Mathew, T Santarius, M D Jenkinson
Journal: Neuro-Oncology (2024)

Abstract BACKGROUND Incidental meningioma is an increasingly common finding. Patients and clinicians need accurate prognostic models to guide individual management. The IMPACT model, a combined cox regression and competing risk model, utilises a patient’s clinical and imaging factors to predict growth and guide decision making after diagnosis. The aim of the international study was to externally validate the IMPACT model. MATERIALS AND METHODS An international multicentre study was established through the British Neurosurgical Trainee Research Collaborative and International Consortium on Meningioma. 33 centres, in 15 countries, submitted baseline and longitudinal clinical (age, sex, performance status and co-morbidity) and imaging (volume, location, T2 peritumoural signal change, venous sinus involvement, and proximity to critical neurovascular structures) data for patients diagnosed with an incidental meningioma in 2009 and 2010. Data collection took place between 12/2020 and 12/2023, providing at least 10 years of follow-up data. RESULTS 1248 patients were included (average 38 patients/centre). Median age was 66 years (IQR 55-77). 987 were female (79.1%). Performance status was 0 at presentation in 593 patients (47.5%). The most common Indications for imaging were headache (24.3%) and audiovestibular symptoms (12.8%). Median meningioma volume at diagnosis was 2.3 cm3 (IQR 0.6-8.8). Meningioma locations were convexity (n=478, 38.3%), parafalcine (n=193, 15.5%), parasagittal (n=188, 13.7%), and skull-base (n=395, 31.7%). Most meningioma did not have T2 peritumoural signal change (n=806, 64.6%). Venous sinus involvement and proximity to critical neurovascular structures were observed in 24.9% and 14.8% of cases, respectively. At initial presentation, 593 (47.5%) entered active monitoring, 347 (27.8%) underwent an intervention (surgery, n=328; SRS/fSRT, n=19) and 455 were discharged (36.5%). During follow-up (median 11 years, range 10-14), an additional 134 patients (14.9%) had an intervention and 406 (32.5%) died (non-meningioma related, n=401; meningioma related n=5). The risk of symptom development in patients who were untreated was 7% (n=63). In patients who were untreated at presentation, the IMPACT score correlated with the risk of requiring an intervention and symptom development (P=0.026 and 0.031, respectively). In patients who underwent surgery, most meningiomas were WHO grade 1 (n=348, 89%) and recurrence free (n=333, 85.4%) after a median follow-up of 5.4 years (IQR 1.7-8.7). CONCLUSIONS This international multicentre study confirms the indolent nature of most incidental meningioma, within the first 10 years of diagnosis. 1 in 7 monitored patients required future treatment. IMPACT appears to correlate well with symptom development and intervention. Further analyses of incidental meningioma growth and intervention outcomes are in progress.