Novel SLC12A2‐ROS1 Fusion in Non‐Small Cell Lung Cancer with a Significant Response to Crizotinib: The Importance of Choosing the Appropriate Next‐Generation Sequencing Assay

Identifying the druggable target is crucial for patients with nonsquamous advanced non‐small cell lung cancer (NSCLC). This article adds to the spectrum of ROS1 fusion cases described in NSCLC. We describe a novel SLC12A2‐ROS1 rearrangement that has not been previously reported in other cancers: a fusion that has clinical and radiological sensitivity to crizotinib. Fluorescence in situ hybridization detected the SLC12A2‐ROS1 fusion and it was confirmed through hybrid capture‐based next‐generation sequencing (NGS); however, the fusion could not be detected by amplicon‐based assay. The success of implementing NGS into routine clinical practice depends on the accuracy of testing. The test's methodological features should then be considered because they significantly affect the results. Given this patient's response to crizotinib, identifying patients with undescribed ROS1 fusions has important therapeutic implications. Key Points This is the first known description of an SLC12A2‐ROS1 fusion. Considering the patient's clinical features and tumor response observed after crizotinib therapy, the authors confirm that this new rearrangement has relevant clinical impact for patients with non‐small cell lung cancer. The success of implementing next‐generation sequencing (NGS) into routine clinical practice depends on the accuracy of the testing. Different assays and NGS platforms can achieve differing results. Each assay's limitations need to be considered to ensure the quality of precision medicine in clinical practice. This case report is the first known report of an SLC12A2‐ROS1 fusion in non‐small cell lung cancer and describes the clinical features and tumor response observed after crizotinib therapy.