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

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.