Dose Escalation by Boosting Radiation Dose Within the Primary Tumor Using 18FDG-PET/CT for Unresectable Thoracic Esophageal Cancer

Inclusion Criteria: 1. Histopathologically proven diagnosis of esophageal squamous cell carcinoma. 2. ECOG performance status 0-1. 3. Able to swallow semifluid diet. 4. Patients must not have received either radiotherapy or chemotherapy. 5. Technically unresectable, medically inoperable, or surgery declined by the patient. 6. SUVmax in the pre-treatment FDG-PET scan \> 5 for the primary tumor and the length of the primary tumor ≤10cm. 7. Normal liver and renal function and adequate bone marrow reservation. 8. Meet the requirements of the dose limitation to the critical organ: V20≤25%，Dmean≤15Gy for lung; Dmax ≤45Gy for spinal cord，Dmean ≤20Gy for liver. 9. Written, signed informed consent. Exclusion Criteria: 1. Other malignancy histology. 2. Any evidence of visceral metastases. 3. Prior radiotherapy to the thorax or systemic therapy for esophageal cancer. 4. Evidence of deep esophageal ulcer or esophageal perforation. 5. Weight loss ≥10% within half year or cachexia. 6. Other co-existing malignancies or malignancies diagnosed within the last 5 years with the exception of basal cell carcinoma or cervical cancer in situ. 7. History of cardiac disease: congestive heart failure \> NYHA class 2, active CAD, cardiac arrythmias requiring anti-arrhythmic therapy or uncontrolled hypertension within the last 12 months. 8. Concurrent uncontrolled medical conditions. 9. Pregnant or lactating women. 10. Drug addiction, alcoholism or AIDS. 11. Uncontrolled seizures or psychiatric, behavioural disorders.