LGG-39. Real-Life Study of the Efficacy and Tolerance of Trametinib in the Treatment of Low-Grade Gliomas in Children With Neurofibromatosis Type 1

Abstract BACKGROUND Low grade gliomas (LGG) are the most common brain tumors in children. Targeted therapies such as the MEK-inhibitor trametinib have revolutionized the management of pediatric LGGs. NF1 mutations generate misregulations in the RAS/MAP kinase pathway, but data on trametinib in type 1 neurofibromatosis (NF1)-related LGG are scarce. Efficacy and safety of trametinib in NF1 patients with LGG need to be further investigated. METHODS This retrospective study included patients with NF1 18 years from two French centers having received trametinib for a relapsing/progressive LGG between March 2020 and July 2022. Treatment efficacy was assessed according to RAPNO criteria, and toxicities and therapeutic exposure were assessed using real-life data collected retrospectively up to July 2023. RESULTS The study enrolled 11 patients, the median age at LGG diagnosis was 3 (1-9) years. All patients previously received a median number of 2 (1-4) lines of chemotherapy. Median age at treatment initiation was 9 (4-13) years. Median duration of trametinib treatment was 9.3 (5.8-24) months. Progression-free survival was 91% at 6 months and 61% at 2 years. Median time to best response was 2.7 (1.1-9) months, including 5 stable diseases, 4 minor responses, and 2 partial responses. Median duration of response was 8.6 (3.7-36.2) months. Adverse events (AEs) occurred in all patients, and 64% of the patient had grade 3 AEs. Skin toxicities and paronychia were the most frequent AEs. Treatment interruption occurred in 55% of the patients, and 3 patients permanently discontinued trametinib due to treatment-related toxicities. Real therapeutic exposure was significantly shorter than theoretically expected (19.6% treatment reduction). CONCLUSION Trametinib showed promising efficacy in NF1 children with relapsing/progressive LGG. Trametinib toxicity remains challenging. Further prospective clinical trials stratified according to molecular alterations are needed to support these preliminary results.