In a study of 103 patients with T790 M positive mutation after the first generation of TKI resistance who were treated with osimertinib showed that the main mutations after osimertinib resistance were EGFR abnormality (25%), MET amplification (16%), TP53 mutation (8%), KRAS mutation (4%), RET fusion (4%), HER2 amplification (4%), and RB1 amplification (6.25%).[45] RB1 mutation indicates the transformation from LUAD to SCLC. The gene discussed is KRAS; the disease is small cell lung carcinoma.