Efficacy of Selpercatinib in Non-small Cell Lung Cancer With Bilateral Internal Auditory Canal Metastases: A Case Report

Selpercatinib is a selective rearranged during transfection (RET) inhibitor approved for treating RET fusion-positive non-small cell lung cancer (NSCLC), demonstrating high efficacy in central nervous system involvement. This case report describes a 65-year-old woman with stage IV lung adenocarcinoma who, after progression on third-line therapy, developed severe neurological symptoms, including hypoacusis, headache, and dizziness, attributed to cerebral and bilateral internal auditory canal metastasis. This study received a favorable opinion from the ethics committee of the Cova da Beira Local Health Unit and informed consent was obtained from the patient in question. Next-generation sequencing identified a RET fusion mutation, leading to the initiation of selpercatinib as a fourth-line treatment. The patient exhibited significant clinical improvement within one week of therapy, including complete hearing recovery. Adverse effects were limited to elevated hepatic transaminases and QT interval prolongation, both of which were effectively managed through dose adjustments. The response to selpercatinib was sustained for over 31 months, at which point new brain metastasis developed, which was possible to address with whole-brain radiotherapy while maintaining targeted therapy with selpercatinib. This case highlights a rare presentation of bilateral auditory canal metastasis in NSCLC with RET fusion, following the failure of platinum-based chemotherapy and immunotherapy. The prolonged progression-free survival and favorable tolerability of selpercatinib, after dose modifications, underscore its potential as an effective treatment option for patients with central nervous system metastasis.