EGFR and lung cancer: Studies have shown that treatment of the first- and second-generation of EGFR-TKIs, including gefitinib, erlotinib, and afatinib, could significantly prolong the progression-free survival (PFS) and improve the response rate of lung cancer patients compared with the standard chemotherapy as initial therapy (Mitsudomi et al., 2010; Wu et al., 2015; Yang et al., 2015).