This prospective observational study (PKU-ESCC-Monitor) aims to characterize the dynamic evolution of esophageal squamous cell carcinoma (ESCC) using integrated multi-omics, including tissue genomics, ctDNA, imaging features, immune profiling and microbiome. Two cohorts will be followed: a peri-operative cohort after standard neoadjuvant therapy and surgery, and an advanced cohort receiving first-line immunotherapy. Clinical outcomes (DFS/PFS/OS) and biomarker dynamics will be analyzed to improve risk stratification and response prediction.