Hypoxia and hypoxia response-associated molecular markers in esophageal cancer: A systematic review

•HIF-1α and CAIX are molecular markers able to estimate hypoxia response in EC.•Population and histological differences affect esophageal hypoxia assessment.•For personalized treatment, tumor microenvironment, stage and histology need to be considered.•Standardization of measuring techniques is crucial for guiding hypoxia research and clinical application in EC.•Hypoxia imaging techniques have the potential to provide individualized information to guide treatment of EC.