EGFR and esophageal squamous cell carcinoma: Previous in vitro kinase assays revealed that afatinib had a higher affinity for wild-type EGFR than gefitinib or osimertinib [27, 28], which were consistent with the current findings that afatinib exhibited better efficacy than other EGFR blockers in ESCC because of its higher potency for wild-type EGFR and broader irreversible ErbB blockade compared with inhibitors that block EGFR alone.