P11.34.A LEPTOMENINGEAL SPREAD IN OLIGODENDROGLIOMAS: INSIGHTS FROM A CASE REPORT AND SYSTEMATIC LITERATURE REVIEW

Abstract BACKGROUND Oligodendrogliomas are a subtype of IDH-mutated gliomas defined by 1p/19q codeletion and generally associated with a more favorable prognosis than astrocytomas. Symptomatic leptomeningeal dissemination in oligodendrogliomas is exceptionally rare. At present, limited information is available regarding incidence and risk factors. METHODS We present the case of a 37-year-old patient diagnosed in 2010 with a right parietal oligodendroglioma, IDH-mutant, and 1p/19q codeleted; Grade 2. In 2014, due to local recurrence and anaplastic transformation, a second surgery was performed, followed by chemo-radiotherapy. In 2022, a growing contrast-enhanced lesion in the hypothalamic region led to a biopsy, which revealed distal recurrence with TERT promoter mutation. Further molecular alterations (CDKN2A/B, MYC) were not found. The patient was treated with proton therapy (total dose: 59,4 Gy), achieving complete radiological resolution. 14 years after the initial diagnosis, in March 2024, the patient developed lumbago and dysesthesia in the lower extremities. Brain MRI was negative; however, spinal MRI revealed extensive leptomeningeal contrast enhancement along the spinal canal, suggesting metastatic spread. Cerebrospinal fluid (CSF) analysis confirmed the radiological suspicion. Rapid clinical deterioration led to the discontinuation of palliative treatment, and the patient passed away in April 2024. Based on this case, we conducted a systematic literature review on PubMed on leptomeningeal spread in oligodendroglioma following PRISMA guidelines We included studies published from 2016 onwards and excluded non-human studies and publications on primary leptomeningeal oligodendroglioma. RESULTS Following the removal of duplicates and studies that did not meet the inclusion criteria, we identified 13 publications reporting cases of leptomeningeal dissemination in oligodendroglioma. Male predominance was observed among the reported cases (ratio 2.33: 1). in 7 cases, the localization of the primitive oligodendroglioma was available. Among those, a high incidence (87.5%) of tumors located adjacent to the ventricular system was found. Of 6 cases with available proliferation index, an elevated Ki 67/MIB-1 index (≥ 15 %) was reported in 83.88 %. It can be speculated that the proximity to the ventricular system and, thus, to CSF pathway, may increase the risk of dissemination. At present, the prognostic value of molecular factors in leptomeningeal seeding remains elusive. CONCLUSIONS The identification of radiological, molecular, and clinical predictive markers is essential for optimizing surveillance strategies and guiding therapeutic decision-making. In patients with oligodendrogliomas located near the ventricular system and exhibiting an elevated Ki-67 proliferation index, MRI screening of the entire neuroaxis may be warranted during follow-up.