e21074 Background: Responses to EGFR-targeted therapy are generally temporary, due to inevitable drug resistance. Although RET fusions have been identified in resistant EGFR-mutant non–small cell lung cancer (NSCLC), their characteristics acquired resistance to EGFR tyrosine-kinase inhibitors (TKIs) are rarely investigated. Methods: We retrospectively reviewed next-generation sequencing data of EGFR+ lung cancer patients, and 8 patients were identified coexisting of EGFR mutations and RET fusion. Their treatment history was collected. Results: The co-occurrence of RET fusion with EGFR oncogenic variations was observed in eight patients, and all of the 8 patients have received previous EGFR-TKI treatment. EGFR mutations were including 4 L858R mutations, 4 exon 19 deletions, and 6 T790M mutations. And the partner genes of RET identified by NGS were including TRIM33 (2/8), GPRC6A (1/8), TLN1 (1/8), KIAA1598 (1/8), SPECC1 (1/8), TRIM24 (1/8) and CCDC6 (1/8). The allelic fractions (AFs) of first-generation EGFR-TKI sensitizing mutations were higher than AFs of EGFR T790M mutations as well as AFs of RET fusion. These RET fusions are fused with rare partner genes, rather than the most common KIF5B in lung cancer. Conclusions: This study extended the knowledge of RET fusion as resistance mechanism to EGFR TKIs in lung cancer. The detection of RET fusions may uncover potential resistance mechanisms of EGFR TKIs, which might inform therapeutic strategies, such as combination-therapy approaches.[Table: see text]
Can EGFR-Tyrosine Kinase Inhibitors (TKI) Alone Without Talc Pleurodesis Prevent Recurrence of Malignant Pleural Effusion (MPE) in Lung Adenocarcinoma