In addition, considering that EGFR T790 M was identified in patient 6 harboring EGFR A763_Y764insFQEA after acquired resistance to gefitinib, we found that EGFR T790 M served as a potential resistant mechanism in EGFR A763_Y764insFQEA positive NSCLC patients and occurrence of both mutations could be targeted by osimertinib. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.