Research Progress on the Mechanism of Gefitinib Resistance and Treatment in Non-small Cell Lung Cancer

Gefitinib, a kind of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs), which is used to the treatment of ever received chemotherapy or unsuitable for chemotherapy in advanced or metastatic non-small cell lung cancer, although the treatment effect is remarkable, in the end, most patients with drug resistance will happen. In recent years, the research showed that the resistant mechanisms are connected with a secondary mutation in exon 20 of EGFR, T790M, the establishment of compensatory signaling pathway and regulating factor to the change of gene expression, and the changes of the tumor microenvironment etc. This review aims to study the mechanisms of drug resistance based on the recent researches, and providing a reference for targeting therapy of tumor.