METHYLATION CLASS AND THE INTEGRATED RISK SCORE IN A COHORT OF 170 MENINGIOMA PATIENTS WITH SUBGROUP ANALYSIS OF RECURRENT, RADIATION-INDUCED AND MULTIPLE MENINGIOMAS

Abstract AIMS To understand the distribution of methylation class (MC) and integrated risk scores (IntRS) within a cohort of meningioma patients, with subgroup analysis of recurrent, radiation-induced and multiple meningiomas. METHODS Analysis of a cohort of 170 meningioma patients between 2018 to 2023. Data collected: neuropathological data, including MC and IntRS (histology, methylation class and chromosomal losses), clinical data such as demograph- ics, extent of surgery, radiotherapy treatment and clinical outcomes. RESULTS Subgroups: 87 primary meningiomas, 30 recurrent meningioma treated with surgery, 14 radiation-induced meningiomas, 6 multiple meningiomas of no clear cause and 33 lost to follow up/other. 30 recurrence cases: 18/30 patients initially grade 1 histology, and 12/30 patients had grade 2 histology. Median final IntRS was 5 [range 0-8]. The distribution and evolution of MC and IntRS will be described, with reference to clinical behaviour (e.g. time to recurrence). In four cases, final MC was benign with IntRS 0-2, despite recurrent disease. 14 cranial irradiation cases (7/14 with multiple meningiomas, 18 surgeries in total): 7/18 were histologically grade 1 (MC - 2 benign, 2 intermediate and 1 malignant, 2 other), 10/18 were grade 2 (MC – 3 benign with IntRS 2- 3, 6 intermediate with IntRS 3-5) and 1/18 was grade 3 (MC malignant, IntRS 7). 3/10 (30%) grade 2 meningiomas had chordoid histology. 6 multiple meningiomas cases: 2/6 had grade 1 histology (MC benign and intermediate), and 4/6 had grade 2 histology (MC benign, IntRS 1-3). 3/4 (75%) patients with grade 2 meningiomas had chordoid histology. CONCLUSION In the majority of cases, MC and IntRS were compatible, and better at predicting behaviour than histological grade. Clinical judgment may be required when the clinical behaviour contrasts with MC and IntRS and caution may be needed in understudied subgroups. Expansion of the cohort with clinical follow up and collaboration across centres is needed.