Rare <b><i>MYH9-ROS1</i></b> Fusion Gene-Positive Lung Adenocarcinoma Showing Response to Entrectinib Treatment: A Case Study

Abstract

The <i>c-ros oncogene 1 (ROS1)</i> fusion gene is a rare genomic alteration detected in nearly 1–2% of lung adenocarcinomas. The major partner genes of <i>ROS1</i> include <i>CD74</i>, <i>SDC4</i>, and <i>EZR</i>. Here, we report a case of <i>MYH9-ROS1</i> fusion gene-positive lung adenocarcinoma, a rare <i>ROS1</i> fusion gene. The patient was a woman in her 40s who was diagnosed with advanced primary lung adenocarcinoma after a thorough examination. Initial genetic testing conducted using mediastinal lymph node biopsy specimens collected by endobronchial ultrasound-guided transbronchial needle aspiration revealed no driver gene mutations, including the <i>ROS1</i> fusion gene. The patient was treated with four courses of immunochemotherapy. As the disease worsened, another genetic test was conducted using FoundationOne^® CDx, and the <i>MYH9-ROS1</i> fusion gene was detected. Multiple lung metastases disappeared after the administration of entrectinib; the response persisted up to a year. Adverse events of rash, dysgeusia, and peripheral edema were observed, and the patient required temporary drug interruption; however, we were able to continue entrectinib following a short-term drug interruption. This is the first report on the effectiveness of entrectinib against lung adenocarcinoma with the rare <i>MYH9-ROS1</i> fusion gene.