RecruitingPhase 2Biological interventionShort-Course Definitive Chemoradiotherapy Combined With Adjuvant or Concurrent Plus Adjuvant Camrelizumab for Locally Advanced Unresectable Esophageal Squamous Cell CarcinomaThis study aims to compare the efficacy and safety of short-course definitive concurrent chemoradiotherapy plus immunotherapy followed by immunotherapy maintenance versus short-course definitive chemoradiotherapy plus immunotherapy maintenance in the treatment of locally advanced unresectable esophageal squamous cell carcinoma, and to exploratorily identify molecular biomarkers associated with treatment efficacy and toxicity.