EGFR and non-small cell lung carcinoma: The result hinted that conservative chemotherapy plus TKI might delay the emergence of TKI resistance, and previous studies had also proved that the combination of gefitinib and pemetrexed prevented TKI resistance mediated by T790M mutation or epithelial-to-mesenchymal transition (EMT) in EGFR-mutant NSCLC cell lines and xenograft models [39].