Swollen feet in advanced stage of lung cancer is mainly related to hypoproteinemia and abnormal reflux, and common causes include malnutrition, obstruction of reflux and abnormal organ function. 1. Malnutrition: Lung cancer in advanced stage will cause a lot of consumption to the body, resulting in hypoproteinemia, which causes a lot of liquid leakage and leads to swelling of the feet. 2. Obstruction of reflux: compression of blood vessels and lymphatic vessels as well as invasion will lead to abnormal reflux condition, which will further lead to fluid leakage and edema. 3. Abnormal function of organs: abnormal function of many organs in the whole body due to tumor, especially liver function and kidney function, will lead to large amount of protein loss, affect osmotic pressure and cause edema. When swelling of feet occurs in late stage of lung cancer, patients are recommended to go to regular hospitals in time and listen to professional doctor’s advice.