Is leptomeningeal dissemination in oligodendroglioma predictable? Evidence from a scoping review

Oligodendrogliomas (ODGs) are IDH-mutated gliomas with 1p/19q co-deletion, typically associated with better outcomes than astrocytomas. Symptomatic leptomeningeal dissemination (LMD) is exceptionally rare, and predictors of its occurrence remain poorly defined. This scoping review aimed to synthesize the available literature on LMD in ODG and identify potential clinical, radiological, surgical, and histo-molecular risk markers.

PubMed/MEDLINE and Embase were systematically searched for studies reporting cases of ODG with LMD. Extracted data included demographics, tumor features, imaging, treatment, molecular markers, and outcomes. Findings were descriptively summarized. An illustrative institutional case was also reviewed.

Of 1719 records screened, 15 studies met inclusion, comprising 48 patients. The mean age at LMD diagnosis was 43.1 years, with male predominance (M: F = 2.4:1). Most patients (39 of 41 patients [85.7%]) had WHO grade 3 ODG at LMD diagnosis. When explicitly stated, LMD was associated with surgical entry into the ventricles (2 of 4 patients [50%]), a Ki-67 index of ≥15% (6 of 7 patients [85.7%]), and contrast enhancement on MRI (4 of 8 patients [75%]). The median time from ODG diagnosis to LMD was 35 months (range 0-274 months). Median survival after LMD was 9.9 months (range 1.8-67.7). Our case reflected these patterns, with 14 years of stable disease followed by rapid decline after LMD onset. Treatments included chemotherapy (23 of 39 patients [58.9%]), radiotherapy (14 of 39 patients [35.9%]), and surgery (12 of 40 patients [30%]), with uncertain benefit.

LMD in ODG is rare but associated with poor prognosis. Features such as grade 3 histology, ventricular involvement, surgical entry into ventricles, contrast enhancement, and high Ki-67 may indicate potential risk markers. These findings support long-term whole-neuroaxis MRI surveillance in selected patients.