Most of the obstruction of superior vena cava reflux is caused by malignant tumors, such as lung cancer, primary mediastinal tumors, lymphoma and metastatic tumors, etc. Chronic mediastinitis and primary superior vena cava thrombosis can also be caused. Its prevention is mostly postoperative prevention, as follows. In order to prevent tumor recurrence, consolidate treatment effect and ensure recovery, regular review is very important. Therefore, tumor patients should be actively reviewed after the treatment. 1. They should follow the instructions of the original treating doctor and go to the treating hospital or tumor specialist hospital for necessary physical examination regularly to find out the problems and treat them in time to prevent the recurrence or metastasis of tumor. 2. Carry the diagnostic examination report before and after tumor treatment to compare with the examination results at the time of review. To facilitate the adoption of reasonable treatment plan. 3. If no sign of metastasis or recurrence is found after the review, you should not give up the opportunity to have a regular review at the hospital next time.