NCMP-11. FACTORS INFLUENCING MANAGEMENT STRATEGY AND CLINICAL OUTCOMES IN LOW-GRADE IDH-MUTANT ASTROCYTOMA: A 10-YEAR INSTITUTIONAL CASE SERIES

Abstract BACKGROUND Low-grade IDH-mutant astrocytomas are rare primary brain tumors that typically affect young adults and slowly progress to more aggressive lesions when untreated. Since lengthy follow-up is required to identify high-risk subgroups and useful therapeutic strategies, consensus recommendations after maximal safe resection are still based on low-level evidence and remain unclear. METHODS Retrospective chart review of all adult patients with a pathological diagnosis of low-grade (grade 2) IDH-mutant astrocytoma from 2013–2023 at a multi-site tertiary care center was performed. Cases without confirmatory IDH-mutation testing or at least 6-month follow-up imaging were excluded. RESULTS A total of 32 patients were included with a mean age of 35.6 years (range: 18–69) and 15 (46.9%) females. Mean follow-up was 40.3 months (range: 8.1–120.7). Preoperative average maximal tumor diameter was 4.1cm (range: 1.4–7cm) with 18 (56.3%) cases involving eloquent cortex. Gross total resection (GTR) was achieved in 12 (37.5%) cases. Observation was the most prevalent postoperative management strategy (n=21, 65.6%), followed by temozolomide-based chemoradiation (n=5, 15.6%), temozolomide alone (n=2, 6.3%), PCV (n=2, 6.3%), radiation alone (n=1, 3.1%), and carboplatin (n=1, 3.1%). Progression of disease (POD) was eventually seen in 17 (53.1%) cases with a median progression-free survival (PFS) of 41.9 months. While GTR was protective against POD (OR:0.14, p=0.019*), initial postoperative management with adjuvant chemotherapy and/or radiation was not (OR:1.09, p=0.907). Additionally, seizures during the follow-up period were significantly associated with POD and a reduced PFS (median 32.5 versus 71.7 months, HR:3.88, p=0.013*). There were no differences in EOR or tumor localization between patients who did and did not have seizures during follow-up. CONCLUSIONS Although limited by sample size, this 10-year series confirms the importance of maximizing EOR for low-grade IDH-mutant astrocytoma and suggests that seizures during follow-up can identify high-risk cases that may benefit from more aggressive treatment.