LGG-38. Unresectable Pediatric Low-Grade Gliomas of the Brain: Targeted Therapy Compared With Standard Chemotherapy as First-Line Treatment

Abstract BACKGROUND Pediatric low-grade gliomas (pLGG) frequently harbor MAPK-pathway mutations that determine poor response to standard chemotherapy (sCt). Targeted agents against BRAF-V600E mutation (MAPK-i) are emerging as molecularly driven treatments. Few studies have compared sCt with MAPK-i. We aimed to compare response and progression-free survival (PFS) of unresectable brain pLGG treated with sCt or MAPK-i. MAPK-i were used in first line or at relapse. METHODS We conducted a single-center observational retrospective study of all brain pLGG consecutively diagnosed and treated at Gaslini Children’s Hospital between January 2008 and December 2021. Treatment was assessed using RAPNO criteria at 6, 12-18 months, and at last follow-up. MRI studies were reviewed by two experienced neuroradiologists. RESULTS Seventy-one patients were enrolled: 66 received sCt and 10 MAPK-i (5 in first line, 5 after sCt failure). All patients who received MAPK-i were BRAF-V600E mutated. Groups were homogeneous for tumor location and dissemination. sCt group was enriched for pilocytic astrocytoma, MAPK-I group for ganglioglioma. sCt patients were younger. SCt lasted 12-18 months, MAPK-i were continuously given. Tumor size reduction was 19.5% at 6 months and 40.5% at 12-18 months for sCt group; 48% at 6 months and 43.5% at 12-18 months for MAPK-i group. SCt determined at least stable disease in 74.2% of patients; 60% of responders reached the best response at 6 months, 40% at 12-18 months. 5y-PFS was 40.3% (median time for progression: 2.5 years). MAPK-i determined at least stable disease in all patients at first evaluation with long-lasting response (median time of follow-up: 5.1 years). CONCLUSIONS In our study sCt was effective in inducing response but prolonged disease control is not always achieved. BRAF-V600E mutated patients upon MAPK-i start gained a rapid disease control with long-lasting response, also if they have been pretreated. Acknowledgement: this study was supported by ARTUCEBA ONLUS.