Characterization of Computed Tomography Imaging of Rearranged During Transfection-rearranged Lung Cancer

Because rearranged during transfection (RET)-rearranged non–small-cell lung cancer (NSCLC) is rare, clarifying the computed tomography (CT) imaging characteristics is crucial. In 21 cases of advanced RET-rearranged NSCLC, the CT imaging characteristics revealed relatively small and solid primary lesions without air bronchogram or cavitation, located as peripheral lung lesions, frequently disseminated to the pleura. These findings could help to better understand the progression pattern of RET-rearranged NSCLC. Rearranged during transfection (RET)-rearranged non–small-cell lung cancer (NSCLC) is relatively rare and the clinical and computed tomography (CT) image characteristics of patients with an advanced disease stage have not been well documented. We identified patients with advanced-stage RET-rearranged NSCLC treated in the Cancer Institute Hospital, Japanese Foundation for Cancer Research, and analyzed the clinical and CT imaging characteristics. In 21 patients with advanced RET-rearranged NSCLC, RET rearrangements were identified using fluorescence in situ hybridization and/or reverse transcriptase-polymerase chain reaction. The fusion partner genes were identified as KIF5B (57%), CCDC6 (19%), and unknown (24%). CT imaging showed that 12 primary lesions (92%) were peripherally located and all were solid tumors without ground-glass, air bronchograms, or cavitation. The median size of the primary lesions was 30 mm (range, 12-63 mm). Of the 18 patients with CT images before initial chemotherapy, 12 (67%) showed an absence of lymphadenopathy. Distant metastasis included 13 with pleural dissemination (72%), 10 with lung metastasis (56%), 8 with bone metastasis (44%), and 2 with brain metastasis (11%). Advanced RET-rearranged NSCLC manifested as a relatively small and peripherally located solid primary lesion with or without small solitary lymphadenopathy. Pleural dissemination was frequently observed.