EGFR and lung cancer: In China, the majority of cancer-related mortality and morbidity is caused by lung cancer [2], about 50% of lung adenocarcinoma patients have EGFR mutations, which always occur on 18 to 21 exons, and the EGFR exon-19 deletion (19del) and EGFR exon 21 L858R mutation (21 L858R) are the two mutations that are most frequently found [3, 4].