EGFR and esophageal squamous cell carcinoma: Previous clinical trials of gefitinib (the COG study) [14, 15] and icotinib (first-generation EGFR-TKIs) [31] demonstrated that EGFR-TKIs exhibited favorable efficacy in ESCC patients with EGFR amplification as detected by fluorescence in situ hybridization (FISH) method.