Systemic treatment is the basic treatment approach to advanced-stage non-small-cell lung cancer (NSCLC), and chemotherapy and targeted treatments are commonly employed in these patients. Recently, positive results achieved with immunotherapy have led to a growing number of treatment options and prolonged survival time. Today, specific tyrosine kinase inhibitors (TKIs), such as erlotinib, gefitinib, and afatinib, which target the epidermal growth factor receptor (EGFR), and the TKI crizotinib, which targets anaplastic lymphoma kinase gene rearrangement, have become the standard treatment among targeted therapies for patients with sensitive molecular anomalies. However, resistance develops against all these agents after a while. Numerous genetic mutations, T790M+ in particular, have been identified as resistance mechanisms against EGFR-TKIs, and researchers are developing specific inhibitors against them. Among those inhibitors, third-generation EGFR-TKIs such as osimertinib and rociletinib have gained prominence due to their high level of effectiveness and low toxicity profile. Besides, systemic chemotherapy and immunotherapy are proper alternatives. A second biopsy during the progression stage and better clarification of the mechanisms causing secondary resistance will enable more successful treatments in the future.
Keywords: Epidermal growth factor receptor; non-small-cell lung cancer; resistance; tyrosine kinase inhibitors.