Effect of Bevacizumab on Radiation-induced Brain Necrosis in Patients With Nasopharyngeal Carcinoma

Inclusion Criteria: * Patients must have received radiotherapy for histologically confirmed nasopharyngeal carcinoma. * Prior irradiation \>/= 6 months prior to study entry. * Radiographic evidence to support the diagnosis of radiation-induced brain necrosis without tumor recurrence. * Age\>/= 18 years. Because on dosing or adverse event data are currently not available on the use of bevacizumab in patients \<18years old. * No prior bevacizumab therapy. * No evidence of very high intracranial pressure that suggests brain hernia and needs surgery. * Fertile women who are willing to take contraception during the trial. * Routine laboratory studies with bilirubin \</=upper limits of normal (ULN), aspartate aminotransferase (AST or SGOT) \< ULN, creatinine \<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. * If with history of seizures, patients should be on anticonvulsant therapy. However, preference will be enzyme-non-inducing anticonvulsants. * Ability to understand and willingness to sign a written informed consent document. * 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: * Patients with any of the following should be excluded: 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. * Evidence of active central nervous system hemorrhage. * History of abdominal fistula, gastrointestinal perforation or intra-abdominal abscess within 28 days prior to study enrollment. * inadequately controlled hypertension (systolic blood pressure (SBP) \> 140 mmHg and/or diastolic blood pressure (DBP) \> 90 mmHg despite antihypertensive medication) * 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. * Evidence of bleeding diathesis or coagulopathy. * Patients who have received steroid therapy for radiation-induced brain necrosis before the study. * History of anaphylactic response to bevacizumab.