EGFR and small cell lung carcinoma: SCLC transformation is one of the mechanisms of drug resistance in TKIs-treated NSCLC patients with EGFR-sensitive mutations, and relevant studies have shown that the incidence of SCLC transformation is 5% ~ 14%, which generally occurs 14-26 months after TKIs treatment, and the median time of transformation is 18 months (4, 10–12).