Response to entrectinib in a malignant glioneuronal tumor with ARHGEF2-NTRK fusion

Glioneuronal tumor (GNT) is a rare tumor. We previously reported a case of high-grade GNT with Rho/Rac guanine nucleotide factor 2 (ARHGEF2)-neurotrophic tropomyosin receptor kinase (NTRK)1 fusion and emphasized the importance of complementary molecular analysis.1 MRI at follow-up showed tumor progression. A cancer gene panel test was performed, and the presence of the ARHGEF2-NTRK1 fusion gene was confirmed. Treatment with entrectinib, an inhibitor of NTRK, was started. MRI follow-ups revealed dramatic responses. However, the patient reported severe general fatigue, and the dose was decreased following the reduced drug protocol. This case highlights the necessity of determining an optimal dose and further profiling the side effects of NTRK inhibitors.