EGFR and lung cancer: Lung cancers with classic EGFR mutations, such as exon 19 deletion (ex19del) and the exon 21 p.Leu858Arg (L858R) point mutation, are responsive to first-to-third-generation EGFR-TKIs, including gefitinib, erlotinib, afatinib, and osimertinib [2–5].