Limitations of the study
Our study has some limitations. First, although most patients with HPSCC were referred for IEE screening from the Department of Otolaryngology, the referral rate was not 100%. Some patients were referred from other physicians when experienced the symptom of dysphagia. This bias may increase the incidence of second primary ESCNs in patients with HPSCC. Second, this was a retrospective study with a relatively small sample size. Larger prospective studies are necessary to confirm the effectiveness of IEE for early detection and treatment of second primary ESCNs in patients with treated HPSCC.