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 non-squamous advanced non-small-cell lung cancer (NSCLC). This case report 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. We detected the SLC12A2-ROS1 fusion by FISH and it was confirmed through hybrid capture-based next-generation sequencing; however, the fusion could not be detected by amplicon-based assay. The success of implementing next-generation sequencing 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 our patient's response to crizotinib, identifying patients with undescribed ROS1 fusions has important therapeutic implications. KEY POINTS: To our knowledge, this is the first description of a SLC12A2-ROS1 fusion. Considering the patient's clinical features and tumor response observed after crizotinib therapy, we can confirm that this new rearrangement has relevant clinical impact for patients with NSCLC. 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.