Capmatinib targeted therapy in MET-fusion driven radiation induced glioma

Introduction: Radiation-induced gliomas (RIGs) can occur in regions of the central nervous system (CNS) previously irradiated for primary malignancies including leukemia, medulloblastoma, and ependymoma. Prognosis is uniformly poor despite treatment with standard of care therapy with radiation ± alkylating chemotherapy. Recent studies have shown that a subset of patients have gene fusions in targetable receptor tyrosine kinases (RTKs) including MET, NTRK2, and RAF1. However, clinical response and outcome to targeted therapy in this patient population have not been described. Methods: We report on two patients with a history of childhood medulloblastoma who developed RIGs harboring MET fusions treated with the selective MET inhibitor capmatinib. Clinical, molecular, and radiographic data are shared to report response and overall survival. Side effects of capmatinib were evaluated and described according to Common Terminology Criteria for Adverse Events version 5 (CTCAE v5.0). A comprehensive literature review was performed to describe all published cases of MET-altered RIGs. Results: Both patients were treated with focal re-irradiation followed by off-label capmatinib targeted therapy. Drug treatment was well tolerated in both patients with the only notable side effect being peripheral edema. Magnetic resonance imaging (MRI) showed significant radiographic response partial response in both as assessed by the Response Assessment in Pediatric Neuro-Oncology (RAPNO) criteria for high-grade glioma (≥50% decrease). Unfortunately, both tumors became resistant and progressed. Overall survival (OS) from diagnosis was 11 and 15 months, respectively, while median OS in historical cohorts is ~9 months. We review the characteristics of MET-altered pediatric high-grade glioma using the Open Pediatric Brain Tumor Atlas (Open PBTA) and published series, which suggests that MET fusions may be enriched in RIGs. Discussion: Our two cases highlight the promising CNS penetration and on-target activity of capmatinib in MET-altered glioma; however, the development of rapid resistance emphasizes the pressing need to develop combination and/or new therapies for RIG.