IL6 and esophageal squamous cell carcinoma: IL6 upregulation in esophageal cancer has been shown before by other authors, and it has been proposed that serum levels of this cytokine could be used as a diagnostic biomarker in ESCC, with higher efficiency than classic tumor markers (carcinoembryonic and squamous cell cancer antigens), and could also predict overall and disease-free survival (31–33).