and fusion as a mechanism of acquired resistance to gefitinib: A case report and literature review.

We report a case with a novel and dual fusion that might be a delicate mechanism for the acquired resistance of epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitor (TKI). A patient with L858R lung adenocarcinoma developed disease progression after 72.7 months of gefitinib therapy; rebiopsy was done, and next-generation sequencing showed the disappearance of the previous mutations. In addition, two new fusions emerged, indicating that the emergence of dual ALK rearrangement may be the underlying mechanism of gefitinib resistance. The patient exhibits an excellent response to second-line alectinib treatment with a significant clinical benefit and a high quality of life. Finally, we summarized previous studies in which fusion is a required resistance mechanism to EGFR-TKI.