Due to the radiosensitivity of the lung, radiation-induced and chemotherapy-induced pneumonitis and pulmonary fibrosis are frequent happened following cancer therapy. It not only compromise cancer treatment, but also influence patient's life qualities and even death. there are no specific treatment modalities for this treatment-induced complication. Bevasizumab (Avastin), a VEGF inhibitor, can attenuate serum high expression VEGF and pulmonary permeability, maybe effective in the control acute pulmonary fibrosis. Patients will be randomized to receive Bevasizumab (7mg/kg iv) on day one and 21, followed by Dexamethasone （10mg iv d 1-10, then 5mg iv d11-15, 2.5mg iv d16-20) or Dexamethasone alone. The thoracic CT, plasma TNF-a, IL-6, VEGF and C-reactive protein are accessed on before treatment, 24 hours after Bevasizumab, 7 days, 4 and 8 weeks. the target sample size is 30 cases.