Mechanisms of Acquired Resistance to Epidermal Growth Factor Receptor Inhibitors and Overcoming Strategies in Lung Cancer

ABSTRACT

Although epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) such as gefitinib and erlotinib show good response and survival benefit in EGFR-mutant lung cancer, acquired resistance inevitably develops which limits the median response duration to around 1 year. Secondary T790M gatekeeper mutation is the most common mechanism representing approximately 50% of resistance. The suggested strategies for overcoming T790M including irreversible EGFR-TKIs, mutant-selective EGFR-TKIs, EGFR dual targeting and HSP90 inhibitors should be further investigated for clinical application. Bypass signals through MET or AXL also contribute to resistance, which lead to development of MET or AXL inhibitors. Other mechanisms such as small cell transformation, epithelial-to-mesenchymal transition, PI3KCA mutation, ERK/HER2 amplification and miRNAs are other suggested candidates awaiting validation. As many resistant mechanisms have been recognized, it is important to obtain tissue samples after resistance to provide appropriate treatment. In this review, recent advances in the understanding of resistance and novel ways of overcoming it are discussed.