So a prospective cohort study has been designed to confirm this hypothesis, patients with advanced pulmonary adenocarcinoma who are stable after two cycles of platinum-based combination chemotherapy are objects of this study, and they can choose to continue the previous treatment regimen according to the guideline or adding bevacizumab to the regimen independently until the progression or intolerance of toxicity, or 4 to 6 cycles of chemotherapy in stable disease. The objective response rate in these two groups who received different treatment is the primary endpoint and the toxicity, quality of life, the progression free survival are the second endpoints.