Inclusion Criteria:
* Voluntary participation and written signed informed consent;
* Age ≥65 years old, gender is not limited;
* Histologically or cytologically confirmed esophageal cancer;
* Elderly patients with stage I-III esophageal cancer who are inoperable or refuse to undergo surgery and can tolerate immunotherapy combined with S-1 and radiotherapy;
* Physical status score ECOG 0-2;
* Expected survival ≥ 6 months;
* no serious abnormalities of haematopoietic, cardiac, pulmonary, hepatic and renal functions and immunodeficiency (Haematology: white blood cells ≥3.5×109/L; neutrophils ≥1.5×109/L; haemoglobin ≥90g/L; platelets ≥100×109/L. Liver and kidney function: total bilirubin ≤1.5 times the upper limit of normal (ULN); AST (SGOT) and ALT (SGPT) ≤2.5 times the upper limit of normal; creatinine ≤1.5 times the upper limit of normal; albumin ≥30 g/L. Coagulation: International Normalised Ratio (INR) or Prothrombin Time (PT) or Activated Partial Thromboplastin Time (APTT) ≤ 1.5 times ULN; if the subject is receiving anticoagulation therapy, PT or INR is acceptable as long as the PT or INR is within the range of the anticoagulant drug formulation. Echocardiographic assessment: left ventricular ejection fraction (LVEF) ≥ low limit of normal (50%). Pulmonary function FEV1 ≥70% of % of predicted value and DLCO ≥60% of % of predicted value).
* Have at least one measurable lesion as judged by RECIST 1.1 criteria.
Exclusion Criteria:
* Distant organ metastases (excluding supraclavicular lymph nodes) as determined by CT evaluation during screening and prior imaging;
* Pre-treatment with oesophageal fistula, perforation, or malignant disease;
* have received prior radiotherapy to the chest;
* having any active autoimmune disease or a history of autoimmune disease (e.g. interstitial pneumonia, uveitis, enteritis, hepatitis, pituitary gland inflammation, vasculitis, myocarditis, nephritis, hyperthyroidism, hypothyroidism (which can be included if hormone replacement therapy is effective), etc.), and a history of immunosuppressive drug use within 28 days, with the exception of the use of hormones for the purpose of dealing with toxicity from radiotherapy;
* Previously received or are receiving other PD-1 antibody therapy or other immunotherapy targeting PD-1/PD-L1, or are currently participating in other interventional clinical studies for treatment;
* Have received other anti-tumour therapy (including herbal therapy with anti-tumour effect) within 4 weeks prior to the first dose of the study; have received long-term systemic immunotherapy or hormone therapy (except physiological replacement therapy, e.g., oral thyroxine for hypothyroidism) within 4 weeks prior to the first dose of the study; and have been treated with other experimental drugs or interventional clinical studies within 4 weeks prior to the first dose of the study;
* Known hypersensitivity to large protein preparations, or to any of the components within toripalimab, S-1 capsules and their preparations;
* Patients with uncontrolled clinical cardiac symptoms or disease such as (1) NYHA class II or higher heart failure, (2) unstable angina pectoris, (3) myocardial infarction within 1 year, and (4) clinically significant supraventricular or ventricular arrhythmias requiring clinical intervention;
* with congenital or acquired immune function defects (e.g., HIV-infected patients), active hepatitis B (HBV-DNA ≥104 copies/ml) or hepatitis C (hepatitis C antibody-positive with HCV-RNA above the lower limit of detection of the analytical method), or active tuberculosis;
* Have an active infection or unexplained fever \>38.5°C within 2 weeks prior to screening (at the investigator's discretion, subjects may be enrolled for fever arising from tumours);
* History of malignancy other than oesophageal cancer within the past 5 years, except for cured basal cell carcinoma of the skin or carcinoma in situ of the cervix;
* In the judgement of the investigator, the subject has other factors that may cause him/her to be forced to terminate the study in the middle of the study, e.g., suffering from other serious illnesses (including psychiatric illnesses) that require comorbid treatment, family or social factors that may affect the safety of the subject or the collection of trial data.
