A Study of SBRT for OligoMetastatic ESCC

Inclusion Criteria: 1. Patients with metastatic esophageal squamous cell carcinoma who have received initial treatment for the primary site including surgery or chemoradiotherapy. Primary tumor site without progression at registration. The sites of allowed metastases are: peripheral lung, central lung, medistinal/cervical lymph node, liver, spinal/paraspinal, osseous, and abdominal-pelvic lymph node. All metastases not resected must be amenable to SBRT. 2. 1-4 radiographically distinct metastases of any distribution in 2 or less allowed anatomical sites. The diameters of lesions should be less than or equal to 5cm. 3. Initial treatment should be completed at least 3 months prior to study registration. 4. All the metastases treated with SBRT should not be treated with surgery, radiation, radio frequency ablation or other regional therapeutic modalities prior to study registration. The other (s) lesions should have been surgically removed. 5. Age ≥ 18. PS ECOG 0-2，wight loss\<30% during the latest 6 months. 6. Evaluation by a radiation oncologist that the patient could tolerate the treatment of SBRT. 7. Patient must provide study specific informed consent prior to study entry. 8. For females of child-bearing potential, negative serum/urine pregnancy test within 14 days prior to study registration. Exclusion Criteria: 1. Progression of primary tumor site at time of registration. 2. Metastases with indistinct borders making targeting not feasible. 3. Known brain metastases. 4. Prior palliative radiotherapy to metastases. 5. Metastases located within 3 cm of the previously irradiated structures: a).Spinal cord previously irradiated \>80Gy(Biological equivalent dose with α/β=2), b).Brachial plexus previously irradiated to \> 100Gy(Biological equivalent dose with α/β=2), c).Small intestine, large intestine, or stomach previously irradiated to \> 90Gy (Biological equivalent dose with α/β=2), d).Whole lung previously irradiated with prior V20Gy \> 30% (delivered in ≤ 3 Gy/fraction), e)Metastasis irradiated with SBRT. 6. Pregnant or breast-feeding women or people during the birth-period who refused to take contraceptives. 7. Drug addiction,Alcoholism or AIDS. 8. Patients with severe organ dysfunction or Acute bacterial or fungal infection who are considered not suitable to enroll the study at the time of registration.