Inclusion Criteria:  Age 70-85 years old, both men and women Histologically confirmed esophageal squamous cell carcinoma located in thoracic segment, treatment naive Stage cT2-4aNanyM0 (AJCC 8 TNM classification) Unresectable, unable to tolerate or refuse surgery and concurrent chemoradiotherapy ECOG PS 0-2 Measurable disease based on Response Evaluation Criteria In Solid Tumors (RECIST) 1.1 No severe abnormalities of the Hematologic system, heart, lung, liver, kidney, and immunodeficiency  Adequate bone marrow and organ function as defined below (excluding the use of any blood components and cell growth factors within 7 days):  Absolute neutrophil count≥1,500/mm3 Platelets ≥ 100,000/mm3 Hemoglobin ≥ 5.6 mmol/L (9g/dL) Serum creatinine ≤ 1.5 x ULN or Creatinine clearance ≥50 mL/min by Cockcroft-Gault estimation Total bilirubin ≤ 1.5 x ULN ALT and AST ≤ 2.5 x ULN Proteinuria < 2+, for subjects with urine protein ≥ 2 + at baseline, urine samples should be collected within 24 hours and urine protein in 24 hours should be ≤ 1g INR or PT or aPTT ≤ 1.5 x ULN Life expectancy more than 6 months Ability to understand and willingness to sign an IRB approved written informed consent document, and capable of proper therapeutic compliance, and accessible to correct follow-up  Exclusion Criteria:  Complete esophageal obstruction that unable to eat fluid and cannot provide necessary nutrition through nasal feeding Patients with obvious ulcer or esophageal perforation or hematemesis Placement of esophagotracheal stents Has a history or current evidence of pulmonary fibrosis, interstitial pneumonia, pneumonoconiosis, drug-associated pneumonia, severe impairment of pulmonary function Has had major surgery within 28 days prior to the start of the treatment Immunosuppressive drugs used within 4 weeks prior to the initial study treatment, excluding local glucocorticoids, or systemic glucocorticoids at physiological doses (i.e., no more than 10 mg/ day of prednisone or equivalent doses of other glucocorticoids); The patient has any active autoimmune disease or a history of autoimmune disease (such as the following, but not limited to: interstitial pneumonia, uveitis, enteritis, hepatitis, hypophysitis, vasculitis, glomerulonephritis, thyroiditis (patients with vitiligo or asthma has been completely relieved in childhood, and do not need any intervention during adulthood can be included; patients with type I diabetes with good insulin control can also be included; hypothyroidism caused by autoimmune thyroiditis requiring hormone replacement therapy can also be included) Has had congenital or acquired immunodeficiency, such as human immunodeficiency virus (HIV) infection, active hepatitis B (HBV-DNA ≥ 104 copies/ml) or hepatitis C (HCV-RNA ≥ 103 copies/ml; For chronic hepatitis B virus carriers, HBV viral load must be < 2000 IU/ml (< 104 copies / ml), and must receive antiviral therapy at the same time before they can be enrolled Known allogeneic organ transplantation (except corneal transplantation) or allogeneic hematopoietic stem cell transplantation Uncontrolled clinically significant disease, including active infection, uncontrolled hypertension, unstable angina pectoris, angina within the past 3 months, heart failure > NYHA II, myocardial infarction within the past 6 months, severe arrhythmias requirement for treatment or intervention, liver/kidney or metabolic disease System infections that require treatment Received a live vaccine within 4 weeks of the first dose of study medication Synchronous or metachronous second primary malignancy. Participants with basal cell carcinoma of the skin, or cervical cancer in situ that have undergone potentially curative therapy are not excluded from the study Patients who have participated in other clinical trials within 30 days Drug addiction, chronic alcoholism and AIDS Patients with uncontrollable seizures or loss of self-control due to mental illness Those with a history of severe allergy or specific physique The investigators judge not suitable for inclusion