EGFR L718Q mutation occurs without T790M mutation in a lung adenocarcinoma patient with acquired resistance to osimertinib.

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) improve the clinical outcomes of EGFR-mutant non-small cell lung cancer (NSCLC) patients significantly, however, acquired resistance occurs almost inevitably. The underlying mechanisms of osimertinib resistance and treatment strategies after resistance remain largely unknown. Here we reported a case of lung adenocarcinoma patient who progressed on osimertinib with EGFR L718Q mutation in the absence of T790M mutation. The patient received icotinib as an exploratory treatment regimen for a short while with stable disease observed. Unfortunately, the therapy was discontinued due to intolerable hepatotoxicity. This is the first clinical report of the use of the effective EGFR-TKI treatment after L718Q-induced osimertinib resistance. The therapeutic regimens for NSCLC patients progressed on osimertinib still require large-scale investigation.