Larotrectinib in NTRK Fusion-Positive High-Grade Glioneuronal Tumor: A Case Report.

Glioneuronal tumors are rare central nervous system tumors with heterogeneous histological and molecular features. While the majority are low grade, a small percentage can behave aggressively. Due to the rarity of these tumors, there is no consensus on how to treat high-grade glioneuronal tumors, and they are often managed similarly to glial tumors. With the advent of molecular profiling, management decisions are increasingly determined by molecular alterations in the tumor rather than the tumor type, which can be a useful approach for tumor types that do not have robust supportive clinical trial data due to low prevalence. We present a case of an 18-year-old patient with a high-grade glioneuronal neoplasm initially treated with craniospinal irradiation, vincristine, and cyclophosphamide. He presented eight years later with a recurrent tumor and was found to be positive for MEF2D-NTRK1 fusion. He was treated with surgical resection and postoperative intensity-modulated radiation therapy (IMRT; 55.8 Gy) with concurrent temozolomide, followed by the NTRK inhibitor larotrectinib. He achieved a radiographic response, with a decrease in residual enhancement and radiographic improvement over the course of treatment. He remained in clinical and radiographic remission for six months. This demonstrates the successful treatment of a high-grade glioneuronal NTRK fusion-positive tumor with larotrectinib, which has only been previously reported once in the literature.