However, the acquisition of the drug resistance to EGFR-TKIs is almost inevitable, and common drug resistance mechanisms include T790M mutation, cMET amplification, etc. One of the rare resistance mechanisms of EGFR-TKIs is the transformation from NSCLC into small cell lung cancer (SCLC), which account for about 3%-15%. The gene discussed is EGFR; the disease is non-small cell lung carcinoma.