Case report: A novel reciprocal ROS1-CD74 fusion in a NSCLC patient partially benefited from sequential tyrosine kinase inhibitors treatment

BACKGROUND: The clinical significance of majority oncogenic novel fusions is still unknown due to scarcity. Reciprocal ROS1 translocation is a rare form of ROS1 fusion and has not yet been clearly analyzed. CASE PRESENTATION: A 44-year-old Chinese woman with a large dimension in the left lobe of the lung was admitted to the hospital with IVB lung adenocarcinoma. It was discovered that intron 28 of ROS1 and intron 6 of CD74 produced a unique reciprocal ROS1 rearrangement. In addition, the dual CD74-ROS1 fusions were discovered using the RNA next-generation sequencing (NGS) findings. Although benefiting from crizotinib and lorlatinib sequential treatment, the overall prognosis of the patient was relatively poor, whose progression-free survival was 4 and 5 months for crizotinib treatment and lorlatinib treatment, respectively. CONCLUSION: In summary, a novel ROS1-CD74 fusion identified by DNA NGS was translated into dual CD74-ROS1 transcripts. Furthermore, this patient with non–small cell lung cancer benefited from consecutive tyrosine kinase inhibitor therapy. Our discovery broadened the range of targetable ROS1 fusions and underlined the importance of sequential DNA and RNA sequencing in identifying uncommon but beneficial fusions, which eventually bring benefits to the patients.