Lung cancer has become one of the leading causes of cancer deaths in humans, and in China, lung cancer is the number one cancer, accounting for more than 20% of cancer deaths, with more deaths from lung cancer each year than from breast, prostate and bowel cancers combined. In recent years, the incidence of lung cancer is on the rise worldwide. According to the latest statistics, the most significant increase in lung cancer among all types of tumors in China in 2005 was 27% for men and 38% for women. Lung cancer has become the number one cancer killer worldwide. The prognosis of lung cancer is closely related to the clinical stage at the time of diagnosis. The 5-year survival rate of early-stage lung cancer patients can reach over 90%, while that of stage I lung cancer patients drops to 60%, while the overall 5-year survival rate of stage II-IV patients decreases from 40% to 5%. Therefore, “early detection, early diagnosis and early treatment” is an important measure to reduce the mortality rate of lung cancer. Can lung cancer be prevented? The development of lung cancer is closely related to lifestyle and habits. Currently, tobacco (including cigarettes, cigars or pipes) has been proven to be the main carcinogenic factor in the development of lung cancer, and about 90% of lung cancers are thought to be caused by smoking. A study of smoking in China conducted by the Chinese Academy of Medical Sciences in collaboration with the University of Oxford in the United Kingdom shows that if the current smoking situation in China remains unchanged, nearly 100 million Chinese men aged 0-29 will die from smoking by 2050 in their middle or old age, and millions of women will die, including 15% of those who die from lung cancer. In general, when smokers quit smoking, their risk of developing lung cancer decreases. In addition to smoking, environmental factors such as exposure to environmental tobacco smoke (passive smoking), and exposure to asbestos or radon (a radioactive gas that occurs naturally in soil and rocks) can also increase the risk of lung cancer. In addition, many bad habits, such as alcohol abuse, excessive consumption of fatty foods, gross fiber and vitamin intake, irregular life, and excessive psychological stress, are closely related to the development of cancer. Are there any symptoms in the early stage of lung cancer? Cough, hemoptysis, chest pain and discomfort are its common symptoms, but they are often ignored by patients. Cough, which is the earliest and most common symptom of lung cancer patients, is not easy to attract attention because it often resembles cold or bronchitis when it starts. Hemoptysis is the second common symptom of lung cancer, which is often caused by the invasion of cancer tissue into the bronchial mucosa, often as blood sputum, and can last for weeks or months or have intermittent episodes. Due to the small amount or intermittent occurrence of hemoptysis, it is easy to be neglected. In fact, about half of those who present with bloody sputum in middle age or older are due to lung cancer. Therefore, it is important not to be paralyzed when unexplained sputum and blood appear. Chest pain accounts for more than half of lung cancer patients, especially in peripheral lung cancer, chest pain can be the first symptom. Therefore, if there is chest pain in a fixed area for unknown reasons, corresponding examination should be conducted as early as possible. What kind of people should have regular checkups? All people over 40 years old, regardless of gender, smoking or non-smoking, and whether they have symptoms or not, should attend annual health checkups as long as they are financially permissible, and one of the important items is chest X-ray. Those who smoke, have family history and feel unwell, especially those who are older than 60 years old, should have regular checkups so that doctors can make early diagnosis of lung cancer and other lung diseases. Is there any method for early diagnosis of lung cancer? In recent years, early diagnosis of lung cancer has become possible due to theoretical and technological advances in the fields of biology and imaging. The limit of detection of nodules in the lung by chest X-ray is greater than 1 cm in diameter, when the tumor may have invaded the bronchial epithelium and vascular epithelium. Compared to plain chest radiography, chest CT is more effective in detecting peripheral lung lesions. The literature reports that low-dose CT is 10 times more sensitive than plain chest radiographs in detecting small nodules in the lung. Currently, this technology has been applied to lung cancer screening studies in Japan and the United States. It has been demonstrated that low-dose CT can detect more lung cancers and more resectable early lung cancers by CT screening than the previous application of chest X-ray plus sputum cytology. Therefore, it has been recommended that smokers older than 60 years of age should undergo annual low-dose spiral CT screening. In recent years, PET-CT has also become one of the effective methods for early diagnosis of lung cancer. It has high sensitivity and specificity for the diagnosis of malignant tumors, especially for peripheral lung cancer with a lesion of about 1 CM and lung cancer with mediastinal lymph node enlargement as the main manifestation. Percutaneous fine-needle aspiration biopsy is extremely accurate in diagnosing malignant nodules in the lung with a sensitivity of 70% to 100%, but it is an invasive test with certain complications, such as pneumothorax and hemoptysis. Sputum cytology is the use of sputum examination to look for cancer cells, especially multiple sputum examinations, and is helpful in diagnosing central tumors originating in the large airways, such as squamous carcinoma and small cell carcinoma. Peripheral tumors originating in the small airways, such as adenocarcinoma, especially those < 2< span=""> cm in diameter, are only occasionally detected by sputum examination, but are important. The sensitivity of sputum examination to screen for early lung cancer is 20% to 30%. The greatest advantage of sputum cytology examination is that it is noninvasive and easily accepted by the examinees, but its greatest limitation is that its positive rate still needs to be improved. In recent years, a new liquid-based cytology technique has been applied to sputum examination, which has greatly improved compared with the traditional method in terms of cell separation and smear, background and cell structure observation, and has significantly improved sensitivity and accuracy. Plain fiberoptic bronchoscopy is the most commonly used diagnostic tool to obtain histological evidence of lung cancer, yet it has limitations in diagnosing early stage lung cancer because these lesions are difficult to determine with the naked eye. Fluoroscopy can significantly improve the detection rate of precancerous lesions and carcinoma in situ and may play an important role in screening and follow-up of people with high prevalence of lung cancer, but its expensive examination cost makes it impossible as a screening tool. The development of lung cancer is a complex lesion process with multi-gene involvement, multi-stage occurrence and long time formation. Theoretically, molecular pathological alterations run through the whole process of human lung carcinogenesis; therefore, they should be used as indicators to monitor the development of lung cancer. However, the current medical science is not sufficient to accurately and timely recognize the molecular pathological changes and their basic rules at the early stage of carcinogenesis, coupled with the difficulties in obtaining materials, which are the keys to the difficulties in early diagnosis of lung cancer. In conclusion, once abnormal lung manifestations are detected, as long as the diagnosis of lung cancer cannot be completely excluded, a very positive attitude should be adopted to make a clear diagnosis as early as possible. As long as early detection can be made and surgery-based comprehensive treatment is taken as early as possible, most patients can achieve better results. Tips 1. Quit smoking or reduce smoking as early as possible, cultivate good living habits and good mentality. 2.Participate in regular medical checkups, especially for the above-mentioned high-risk groups, at least once a year. 3.Patients with irritating cough, chest pain and hemoptysis should go to hospital for examination as early as possible.