Lung cancer has become the number one malignant tumor threatening human health, but unfortunately, most lung cancer patients are found late in life and miss the best time for treatment and lose the opportunity for surgery. For the elderly, the most easily ignored early lung cancer symptom is recurrent lung infections. As the tumor compresses the trachea, bronchus or fine bronchus, the lung secretions at the distal end of the compression cannot be eliminated through the trachea (i.e. sputum accumulates inside the lung, how dirty you think it is), making frequent lung infection. After anti-inflammatory treatment, the fever subsides, the shadow disappears, and the patient thinks he is cured, but after a while the fever and infection will occur again, because the mass compression is not released. Therefore, if recurrent lung infections occur, one should be alert and have at least a chest CT because some areas are dead spots on chest X-rays and not easily detected by doctors. Besides recurrent lung infections, early symptoms of lung cancer include, pain in the chest, blood in sputum or hemoptysis, difficulty in breathing, hoarseness, etc., which should be promptly sought for treatment.