Treatment of Bevacizumab Followed by Steroid in RN

Inclusion Criteria: 1. Patients must have received radiotherapy for histologically confirmed nasopharyngeal carcinoma. 2. Prior irradiation \>/= 6 months prior to study entry. 3. Radiographic evidence to support the diagnosis of radiation-induced brain necrosis without tumor recurrence. 4. Age\>/= 18 years. Because on dosing or adverse event data are currently not available on the use of bevacizumab in patients \<18years old. 5. No prior bevacizumab therapy. 6. No evidence of very high intracranial pressure that suggests brain hernia and needs surgery. 7. Fertile women who are willing to take contraception during the trial. 8. Routine laboratory studies with bilirubin \</=2 \* upper limits of normal (ULN), aspartate aminotransferase (AST or SGOT) \< 2 \* ULN, creatinine \<1.5 \* ULN, red-cell count \>/= 4,000 per cubic millimeter; white-cell count \>/=1500 per cubic millimeter, platelets \>/= 75,000 per cubic millimeter; Hb \>/=9.0. PT, APTT, INR in a normal range. 9. If with history of seizures, patients should be on anticonvulsant therapy. However, preference will be enzyme-non-inducing anticonvulsants. 10. Ability to understand and willingness to sign a written informed consent document. 11. The patient has no active bleeding or pathological condition that carries a high risk of bleeding; there is no evidence of serious or non-healing wound, ulcer or bone fracture. Exclusion Criteria: 1. evidence of metastatic disease; 2. evidence of tumor invasion to major vessels(e.g. the carotid); 3. history of bleeding related to tumor or radiotherapy during or after the completion of radiation. 4. Evidence of active central nervous system hemorrhage. 5. History of abdominal fistula, gastrointestinal perforation or intra-abdominal abscess within 28 days prior to study enrollment. 6. inadequately controlled hypertension (systolic blood pressure (SBP) \> 140 mmHg and/or diastolic blood pressure (DBP) \> 90 mmHg despite antihypertensive medication) 7. Severe complications: 1) History of large vessel cerebrovascular accident (CVA) within 6 months; 2) Myocardial infarction or unstable angina within 6 months; 3) New York heart association grade II or greater congestive heart failure; 4) Serious and inadequately controlled cardiac arrhythmia; 5) Significant vascular disease (e.g. aortic aneurysm, history of aortic dissection); 6) Clinically significant peripheral vascular disease; 7) severe infection. 8. Evidence of bleeding diathesis or coagulopathy. 9. Patients who have received steroid therapy for radiation-induced brain necrosis before the study. 10. History of anaphylactic response to bevacizumab.