EPID-05. LEPTOMENINGEAL METASTASES IN GLIOMA REVISITED: HIGH INCIDENCE AND THEIR MOLECULAR PREDICTORS BASED ON RECENT IMAGING AND MOLECULAR DIAGNOSTICS

Abstract

Abstract BACKGROUND Leptomeningeal metastases (LM) in glioma has been underestimated due to low incidence and lack of reliable imaging. This study aimed to investigate a real-world incidence of LM using a CSF-sensitive MR imaging technique and analyze molecular predictors for LM in the molecular era. METHODS Total 1,405 adult glioma patients underwent post-contrast fluid attenuated inversion recovery (FLAIR) imaging at initial diagnosis and during treatment monitoring between March 2001 and October 2021. Molecular data included isocitrate dehydrogenase (IDH) mutation, 1p/19q co-deletion, H3 K27M alteration, and O6-methylguanine-methyltransferase (MGMT) promoter methylation status. Multivariable logistic regression analysis for LM development was performed in molecular data, clinical data, and imaging characteristics. Median overall survival (OS) was compared between patients with and without LM using Kaplan-Meier survival curves and log-rank test. RESULTS LM was identified in 16.2% of glioma (228 of 1405), with 7.8% (110 of 1405) at initial diagnosis, and 8.4% (118 of 1405) at recurrence. Among molecular diagnostics, IDH-wildtype (odds ratio [OR] 3.14, P = .001) and MGMT promoter unmethylation (OR 1.43, P = .034) were independent predictors of LM. WHO grade 4 (OR 10.52, P < .001) and nonlobar location (OR 1.54, P =.048) were associated with LM at initial diagnosis, whereas IDH-wildtype (OR 5.04, P < .001) and H3 K27M alteration (OR 3.39, P =.003) were significantly associated with LM at recurrence. Patients with LM had a worse median OS than those without LM (16.7 vs. 32.0 months, log-rank test; P < .001). CONCLUSIONS CSF-sensitive MR imaging diagnostics aid diagnosis of LM and reduced an underdiagnosed condition in adult gliomas. Molecular markers affect LM at initial diagnosis and at recurrence, and patients with aggressive molecular markers warrant imaging surveillance of LM.