Patients with esophageal cancer that had metastatic lesions after been treated with definitive surgery or chemoradiotherapy are being asked to participate in this study. 1. To observe immunity-mediated tumor response after Stereotactic Body Radiation Therapy(SBRT) of a metastatic site in metastatic esophageal cancer patients. 2. To induce the efficacy (effectiveness) of a new combination of therapy, SBRT and thymalfasin for heavily pretreated, metastatic esophageal cancer patients; This study will help find out what effects (good or bad) the combination of radiotherapy and thymalfasin has on metastatic esophageal cancer.

1. To observe immunity-mediated tumor response after Stereotactic Body Radiation Therapy(SBRT) of a metastatic site in metastatic esophageal cancer patients. 2. To induce the efficacy (effectiveness) of a new combination of therapy, SBRT and thymalfasin for heavily pretreated, metastatic esophageal cancer patients; Eligible are patients with metastatic esphageal cancer who have achieved stable disease or have disease progression after systemic therapy (surgery or definitive chemoradiotherapy) and have at least two measurable sites of metastatic lesions. Extent of metastatic disease is recorded both at CT and PET/CT scanning. Radiation is given during combined therapy to one of the lesions, 25Gy in 5 fractions over one week interval with SBRT, conformally to maximally spare normal tissue or organ. Thymalfasin treatment is given twice a week with an interval of 3-4 days each week for a total of 8 weeks. Tumor response is evaluated by assessing clinical and CT/MRI response for all of the measurable metastatic sites. A Phase II clinical trial based on an optimum two-stage Phase II Simon design is used to conduct this pilot study. Ten patients will be treated in Stage one; if there are no tumor responses, the trial will be terminated. If there are one or more tumor responses in Stage One, the trial will proceed to enroll an additional 19 patients.