The purpose of this study is to determined the best definitive radiotherapy dosage for patients with locally advanced esophageal squamous cell carcinoma.

Inclusion Criteria:

• Joined the study voluntarily and signed informed consent form;
• Age 18-75 years; both genders
• Esophageal squamous cell carcinoma confirmed by pathology.
• No radiotherapy, chemotherapy or other treatments prior to enrollment
• Locally advanced esophageal squamous cell carcinoma (T1N1-3M0, T2-4NxM0, TxNxM1 (supraclavicular lymph node metastasis only) (AJCC 8th)
• Use of an effective contraceptive for adults to prevent pregnancy.
• No severely abnormal hematopoietic, cardiac, pulmonary, renal, or hepatic function. No immunodeficiency.
• WBC ≥ 3.5*109/L, Hemoglobin ≥ 9 g/dL, Neutrophils ≥ 1·5*109/L, Platelet count ≥ 100*109/L, ALAT and ASAT < 2·5 * ULN, TBIL < 1·5 * ULN, and Creatinine < 1·5 *ULN.
• ECOG 0-2.
• Life expectancy of more than 3 months.
• Agreement of PET/CT accessment at 25-28 radiotherapy fraction.

Exclusion Criteria:

• Total radiotherapy dose cannot reach 61.2Gy/34Fx in the condition of the nomal tissue dose complying to the standard criteria.
• Esophageal perforation, or hematemesis.
• History of radiotherapy or chemotherapy for esophageal cancer.
• History of surgery within 28 days before Day 1.
• History of prior malignancies (other than skin basal cell carcinoma or cervical carcinoma in situ with a disease-free survival of at least 3 years).
• Participation in other interventional clinical trials within 30 days.
• Pregnant or breast-feeding women or fertile patients who refused to use contraceptives.
• Drug addiction, alcoholism or AIDS.
• Uncontrolled seizures or psychiatric disorders.
• Any other condition which in the investigator's opinion would not make the patient a good candidate for the clinical trial.