Identification of A Novel FRK-ROS1 Fusion Variant in Advanced Non-Small Cell Lung Cancer with Brain Metastases and Remarkable Response to Crizotinib

ROS1-rearranged non-small cell lung cancer (NSCLC) is a subset of NSCLC patients with unique malignant behavior and clinical course. Crizotinib, a multi-targeted ALK/ROS1/MET tyrosine kinase inhibitor (TKI), has promising significant activity in NSCLC with ROS1-rearrangement. The next-generation sequencing (NGS) is commonly used to identify the “druggable” genetic alterations in clinical practice. We identified a novel ROS1 fusion variant (FRK-ROS1) in a de novo stage IV NSCLC patient by NGS testing. This novel ROS1-rearrangement is generated by the fusion FRK to ROS1. The patient was remarkably responsive to crizotinib including the brain metastasis. A 29-year-old male never-smoker with chief complaints of back pain with a lumpy and flaky soft tissue mass in the upper right lobe of the lung and diffuse ground-glass shadow in both lungs e IV (cT4N3M1b). A CT-guided biopsy revealed the predominant adenocarcinoma and partial mucinous adenocarcinoma. By using next-generation sequencing (NGS) assay, we found that the tumor had FRK-ROS1 fusion rather than other actionable mutations. In that case, the patient took the first-line crizotinib and experienced a remarkable tumor response to it and tolerance well until written. FRK-ROS1 is a novel ROS1 fusion variant in NSCLC identified by NGS testing and the first-line crizotinib showed excellent performance in all lesions including the brain metastasis.