EGFR and neoplasm: First, because two ESCC cell line model was used, expanded preclinical and clinical research are required in various ESCC animal models and clinical patients with tumors expressing varying level of EGFR to validate the association between 64Cu-PCTA-cetuximab accumulation in tumor lesion and prognosis after cetuximab immunotherapy and to establish PET signal cutoff value for target selection as imaging biomarker.