Targeting EGFR in Lung Cancer: Current Standards and Developments

Lung cancer is the second most common malignant tumor and the leading cause of cancer death. Epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) is a distinct subtype of lung cancer comprising approximately 15–40% of non-squamous tumors. The development of first- and second-generation EGFR tyrosine kinase inhibitors (TKIs) has been a significant step forward in the treatment of patients with EGFR-mutant tumors, and over the last few years has been the therapy of choice in the initial management of patients with activating mutations in EGFR, with some differences in efficacy and toxicity profile. Up to 50% of patients treated with first- and second-generation TKIs develop an EGFR exon 20 T790M mutation at the time of progression. In this context, osimertinib has shown a great benefit in terms of progression-free survival (PFS) in the second-line setting, including central nervous system metastasis control. The FLAURA trial, which compared osimertinib to first-generation inhibitors as first-line therapy, showed a clear PFS advantage for osimertinib and a trend towards an increased overall survival (OS) assessed by investigator review. Although T790M mutation is the most common mechanism of resistance to first- and second-generation EGFR TKIs, other EGFR-dependent and -independent mechanisms have been described, such as HER2 and MET amplifications or BRAF and MEK mutations. Some mechanisms of resistance to osimertinib and other third-generation TKIs have also been described. Several fourth-generation TKIs, targeted drug combinations and immunotherapy strategies are under investigation to overcome resistance to EGFR TKIs in order to improve EGFR-mutant NSCLC patient outcomes.