INNV-37. Real-world observation rates and treatment patterns in IDH-mutated glioma: implications for targeted therapy use

Abstract INTRODUCTION The approval of vorasidenib marks a paradigm shift in the management of IDH-mutated (mIDH) gliomas. This study characterizes treatment patterns (including observation rates), following surgery for mIDH glioma during a period preceding vorasidenib approval, aiming to quantify the population that may benefit from vorasidenib. METHODS This retrospective study analyzed grade 2/3 mIDH glioma patients aged >12 years from the National Cancer Database (2018–2021), which captures >85% of U.S. malignant brain tumors. Included patients underwent surgery within 90 days of diagnosis without prior treatment. Observation (no treatment ≥90 days post-surgery) and treatment patterns (radiation, chemotherapy) were analyzed using descriptive statistics. Kaplan-Meier models were used to estimate treatment initiation rates, with individuals censored at time of death. RESULTS A total of 5,894 patients with mIDH glioma were identified, with 61% having grade 2 and 39% grade 3 tumors; the median (IQR) age at diagnosis was 39 (31-50) years. The overall initial observation rate was 34.9%, with rates of 51.6% in grade 2 and 16.7% in grade 3 tumors. Observation occurred in 33.5% of astrocytoma and 38.7% of oligodendroglioma cases, and in 30.1% of patients with subtotal resection and 39.3% with gross-total resection. By 90 days post-surgery, 63% of patients had initiated therapy, peaking to 70% by 180 days. The most common first intervention was concurrent chemoradiation (27.6%), followed by radiation only (25.8%) and chemotherapy only (17.6%). CONCLUSION Historical management patterns show a substantial proportion of patients with mIDH glioma were managed with observation, suggesting an unmet need for an effective early intervention, while most others received early radiation or chemotherapy, highlighting the need for less-toxic alternatives given their well-established long-term adverse effects. Vorasidenib, as recommended by guidelines, offers an early, effective, low-toxicity treatment option across these groups. These data provide a baseline for assessing the evolving role of vorasidenib in mIDH glioma.