Lung cancer can cause edema, mainly depressed edema, the causes of which include severe hypoproteinemia, cardiogenic edema, nephrogenic edema, anemia, etc., as follows: Firstly, severe hypoproteinemia: it is mainly due to the high consumption of cancer and the lack of nutrition of patients with little food, which leads to the decrease of albumin concentration in blood, and manifests itself in the depressed edema in the lower part of the body, mainly in the double lower limbs. Second, cardiogenic edema: it is mainly because lung cancer pericardial metastasis leads to a large amount of pericardial effusion, which restricts cardiac diastole, impairs cardiac function, and stagnant blood in body circulation, thus leading to double lower limbs edema. In addition, the side effects of drugs after chemotherapy for lung cancer will also damage heart function and lead to cardiogenic edema. Thirdly, nephrogenic edema: it is mainly because of kidney damage after chemotherapy of lung cancer, which leads to the restriction of water discharge from kidney and edema in eyelid area. Fourthly, anemia: due to the side effect of bone marrow inhibition after chemotherapy, or poor nutrition of patients in advanced stage, this will lead to severe anemia, which will be manifested as edema of the whole body.