Inclusion Criteria:
1. age: 18 - 75 years
2. gender: both sexes, as balanced as possible
3. patients with clinically confirmed TNM 8th stage II-III ESCC by histopathology and are not suitable for surgery
4. patients receive neoadjuvant immunochemotherapy, followed by radical CCRT combined with immunotherapy and finally adjuvant immunotherapy
5. Eastern Cooperative Oncology Group (ECOG) score: 0-1
6. the functional condition of the organ meets the following requirements- haematological indicators: absolute neutrophil count ≥ 1.5 \* 109/L, platelet count ≥ 100 \* 109/L, haemoglobin count≥ 9 g/dL; good coagulation: platelet count ≥ 100 x 109/L. Liver: total bilirubin ≤ 2 times the upper limit of normal, ghrelin and ghrelin ≤ 2.5 times the upper limit of normal. Renal: creatinine ≤ 1.5 times the upper limit of normal, or creatinine clearance ≥ 60 mL/min (calculated by the Cockcroft-Gault formula)
7. women of childbearing age must have a urine pregnancy test with a negative result within 7 days prior to starting treatment
8. patients understand and voluntarily sign the informed consent form
Exclusion Criteria:
* (1) patients have been diagnosed or treated for another malignancy within 5 years prior to the start of this study (2) adenocarcinoma, mixed adenosquamous or other pathological types of esophageal cancer (3) any unstable systemic disease, including: active infection, uncontrolled hypertension, unstable angina, angina pectoris starting within the last 3 months, congestive heart failure (≥ New York Heart Association \[NYHA\] class II), myocardial infarction (6 months prior to enrollment), severe arrhythmia requiring medication, liver, kidney or metabolic disease (4) with known or suspected active autoimmune disease (5) previous treatment with anti-PD-1, anti-PD-L1, anti-PD-L2, anti-CD137 or anti-CTLA-4 antibodies or any other antibodies or drugs that specifically target T-cell co-stimulation or checkpoint pathways (6) known history of testing positive for human immunodeficiency virus (HIV) or known to have acquired immunodeficiency syndrome (AIDS) (7) female patients who are pregnant or breastfeeding (8) other conditions deemed unsuitable for enrolment by the investigator
