Early detection and early diagnosis are the important aspects of lung cancer prevention. Only through early diagnosis, early detection and early treatment can we effectively stop the development of the disease. However, regrettably, although more than 90% of lung cancer patients have symptoms in early stage, they are not specific symptoms of lung cancer, so they are often not taken seriously by patients or even by doctors, resulting in delayed diagnosis and treatment, and are already in the middle and late stage after detection, which makes treatment difficult and ineffective. This suggests that if elderly people have the following early symptoms, they should think of the possibility of lung cancer and need to go to hospital for examination. Cough: Cough caused by tumor lesions and their secretions stimulating bronchial mucosa is usually the first symptom and early warning sign of lung cancer. Of course, cough is not a unique symptom of lung cancer, but some other diseases may also cause cough. However, if the cough is irritating and dry and does not improve after one to two weeks of anti-inflammatory treatment, it should be alerted to the possibility of lung cancer, which should be taken seriously by patients and doctors. 2.Blood sputum: It is a common first symptom of lung cancer and is the initial warning sign of lung cancer. It is often caused by the ulceration of cancer lesions and is manifested as blood in sputum or blood clots, while massive hemoptysis is rare. Therefore, people of middle age or above, both men and women, should think of the possibility of lung cancer if they have no previous history of hemoptysis but suddenly appear unexplained bloody sputum. 3. Chest pain: Initial chest pain is usually irregular chest tightness, pressure or dull pain, sometimes the patient cannot even describe the nature and specific location of the pain, but this is exactly a symptom of lung cancer at the early stage. Therefore, for people above middle age, once they feel chest pain, they should be examined at an early stage and should not let it go easily. If the chest pain is severe or persistent, or has been fixed in a certain area, it means that the lung cancer lesion has invaded outward and involved the pleura and chest wall, which is more serious. 4.Shortness of breath: shortness of breath is certainly not a specific symptom of lung cancer, but it is a significant symptom in the early stage of lung cancer. Shortness of breath can be caused by pneumonia, atelectasis, malignant pleural effusion, diffuse alveolar lesions, etc. caused by obstruction of respiratory tract by tumor materials. At this time, the possibility of lung cancer should be thought of when people above middle-aged have persistent and progressively heavy shortness of breath. 5.Fever: When lung cancer lesions block large bronchi or invade the bronchial wall and cause bronchial narrowing, the secretions in the distal bronchi may accumulate and cannot be emptied, which may cause generalized fever due to infection. Although this kind of fever is also not a symptom specific to lung cancer, it should not be easily “diagnosed” as a cold or general bronchitis if it is a middle-aged person or above, but should be examined in detail. Especially if the fever is accompanied by intrapulmonary shadow (X-ray manifestation), it should not be let off easily and the real cause should be searched carefully. In addition to the general symptoms mentioned above, some patients may have some extra-pulmonary symptoms, or metastatic symptoms due to early metastasis. However, for the majority of lung cancer patients, until the late stage, the systemic symptoms are not obvious, and there is usually no wasting, weakness, or obvious respiratory dysfunction. Therefore, it is important for people over 40 years old, especially those who are at high risk of lung cancer, to grasp some early warning signs of lung cancer, and once there are warning signs, they should seize them and seek medical treatment in time to trace them to the end. The lung cancer detected by such warning signs is mostly in the early stage, and the treatment effect is better and the prognosis is better.