Lung cancer (lung cancer) refers to primary bronchoplmonary carcinoma, which is the most common malignant tumor of the lung. In recent years, the incidence of lung cancer at home and abroad has been increasing. The five-year survival rate of lung cancer is directly related to whether it is detected early or not. The five-year survival rate of stage I lung cancer is 45%-50%, which can reach 80-90% if surgery is performed, while in stage IV, the five-year survival rate falls to 1-5%. Unfortunately, however, more than half of lung cancer patients are already stage IV lung cancer by the time they are diagnosed. Early stage of lung cancer needs to be screened by doctors at all levels based on their judgment of clinical symptoms, and not only specialists, but also community doctors and family doctors responsible for general practice should pay attention to it. It is important to note that early symptoms are equally important for smokers and non-smokers. Currently, 50% of lung cancer patients are ex-smokers and 15% are smokers. And lung cancer is increasing in younger patients, with 1.2%-6.2% of lung cancer patients in the United States being younger than 40 years of age in 2014. What are the early clinical symptoms of lung cancer? 1. Cough About one-half to two-thirds of patients have cough as the initial symptom. Many patients have cough symptoms, especially irritating dry cough, but this symptom is often easily ignored by doctors and patients or classified as other causes. Cough symptoms are not too common and can easily be missed. If the cough persists for more than two or three weeks, or if there is a change in the nature of the cough, it must be taken seriously. In addition to the need for differential diagnosis with respiratory allergies and respiratory infections, patients with asthma, chronic obstructive pulmonary disease (COPD), allergies, or gastroesophageal reflux who have cough symptoms due to their primary disease need to be carefully identified when diagnosing. 2. Occasional blood in sputum About one-third of the patients with this as the first, if the sputum is checked for cancer cells at this time, the positive rate can reach 60-80%. 3.Shortness of breath during action As another early symptom of lung cancer, this symptom is easily considered to be caused by old age, poor physical condition or obesity. If patients feel shortness of breath during daily activities without cardiovascular disease, they need to pay attention to lung cancer screening. 4. Chest pain One-third to three-fifths of patients present with chest pain. Lung cancer, especially peripheral lung cancer, may invade the pleural nerves and cause chest pain, – a symptom that may even precede coughing and shortness of breath. If painful symptoms are present in these areas without primary injury, pain that does not resolve or worsens, especially painful symptoms that worsen with coughing and breathing, require close attention. Up to 40-50% of lung cancer patients have a chest pain condition at the time of diagnosis. 5. Recurrent infections (bronchitis and pneumonia) It is not uncommon for patients with recurrent pneumonia or bronchitis to be diagnosed with lung cancer clinically. If the tumor is close to the airway, it can compress the airway or directly obstruct the airway causing obstructive pneumonia, which is poorly treated by anti-infection therapy or is aggravated again after getting better. Long-term smoking or COPD can also cause lung infection and bronchitis, which are also high risk factors for lung cancer. 6.Extrapulmonary symptoms include: osteoarthropathy, ectopic endocrine syndrome Sometimes even seemingly unrelated symptoms are associated with lung cancer, especially in patients who smoke. For example, 1.7% of lung cancer patients will have knee pain in the early stage. In addition, a combination of symptoms such as fatigue, loss of appetite, unexplained weight loss and even the onset of depression may indicate lung cancer. Statistics show that 25% of lung cancer patients have no specific symptoms when they are diagnosed with lung cancer, and many are found only after a CT or X-ray of the chest for other reasons.