Pediatric Low Grade Glioma - MEKinhibitor TRIal vs Chemotherapy

Plain-language summary

Pediatric low-grade glioma (PLGG) is a heterogeneous group of WHO grade I and II brain tumors, associated with a 10-year overall survival of 90%. It is the most common form of primary central nervous system (CNS) tumor arising during childhood, adolescence and young adulthood, accounting for over 30% of CNS tumors in this age group. A large group of PLGG patients will benefit from a complete resection of their tumor. Nevertheless, PLGG can occur anywhere and can be in some locations associated with neurological symptoms, unresectable or radiological progressive tumors that need medical treatments rapidly to avoid long-term sequelae. The current problem during this first line therapy is to improve tumor response, overall survival rate, as well as progression free survival. In our study, we will focus on a specific group of PLGGs without any congenital NF1 mutation and with a wild-type BRAF gene in the tumor. In this subgroup, for instance, the PFS is not increasing anymore above 50% at 3 years independently from the chemotherapeutic scheme. The two current standard therapies are carboplatin plus vincristine during 81 weeks or a weekly IV administration of vinblastine during 70 weeks. The most recent Canadian approach with vinblastine seems to have the same PFS rate, but with a better daily tolerance and less toxicities than the carboplatin/vincristine combination. Therefore, it is becoming the new standard approach in those patients. Nevertheless, we need to improve more their outcome with less recurs and a better first-line tumor response. The recent molecular discoveries involving the Ras/mitogen-activated protein kinase pathway in those PLGG is opening a new era with specific targeted therapies that might be the key to improve their survivals and giving hope to less treatment lines and a better tumor response. Therefore, we designed a prospective open randomized phase II study, named PLGG-MEKTRIC, comparing the experimental arm (a daily MEK inhibitor, Trametinib, Mekinist©) to a standard arm comprising weekly vinblastine during 18 courses of 4 weeks each. The study will enroll 134 patients with a PLGG during childhood, adolescence or young adulthood with no NF1-related disease and without any BRAFv600 mutation located in brain or spine. 67 patients, in each treatment arm, are planned to be enrolled to answer our primary objective. This primary objective will be to determine in the experimental arm a 20% superiority of the 3-year PFS rate in comparison with the standard treatment administered during 18 courses (e.g. 72 weeks). A stratification of the patients will be done in both arms based on molecular tumor results and brain/spine locations to obtain two equivalent arms to be analyzed. The recruitment time will be 36 months and the complete follow-up of each patient will last 3 years. The secondary objectives will be in both arms: the tumor response rate at 24 and 72 weeks of treatment, the 3-year PFS and OS rates and the frequency of AE/SAE/SUSAR (Adverse Event/Serious Adverse Event) based on CTCAE criteria during the 3 years after the first administration. A Quality of Life (QoL) assessment, based on PEDsQL questionnaires, at 24 weeks, at the end of treatment and 3 years after 1st treatment administration in both arms will be part of this study. Finally, 3-year PFS and OS will be analyzed according to molecular biomarkers and visual assessment (LogMar scale) in each arm. An economic analysis is also planned as an ancillary study to determine a cost effectiveness of the best arm and complementary ancillary molecular studies are already organized. In the future, we hope to push forward this new-targeted therapy as a referenced first line treatment of pediatric PLGG to obtain the best tolerance and positive long-term impact and to extend our knowledge of MEK inhibitor impact in molecular subgroups and in optical pathway locations. We also plan to do a "switch" strategy in patients relapsing in standard arm and we will propose systematically to those patients the experimental treatment (MEK inhibitor ).

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