Malignant tumors that are more closely related to smoking include lung cancer, oral cancer, throat cancer, esophageal cancer, stomach cancer, colon cancer, liver cancer, pancreatic cancer, bladder cancer, skin cancer, and kidney cancer. Among them, the most closely related and well known is lung cancer. The international medical community recognizes that smoking is the main culprit of lung cancer. The prevalence of lung cancer among smokers is 3-15 times higher than that of nonsmokers, with some reports reaching up to 30 times. Among the more than 8.3 million deaths in China each year, smoking is the cause of more than 1 million, including about 600,000 lung cancer deaths. Some data show that 87% of lung cancer deaths are caused by smoking and passive smoking. The 600,000 deaths from lung cancer caused by smoking represent only a small fraction of the hundreds of millions of smokers and passive smokers, and the chances of eventually dying from lung cancer after decades of smoking are only a few percent, even though they are very high. Therefore, when smokers have signs such as irritating dry cough and bloody sticky sputum, they often do not care, and most lung cancer patients are already in advanced stage when they are diagnosed, losing the best time for radical treatment, which is the main reason why lung cancer mortality rate is the first among all kinds of malignant tumors. Therefore, although getting cancer is a low probability event, it is 100% for individuals once they have it. Instead of regretting the disease, it is better to quit smoking as soon as possible to prevent it from happening. There is a smoking index formula, which you can calculate: number of cigarettes smoked per day x number of years of smoking = smoking index. In lung cancer research, people with a smoking index of 400 or more, or those who smoke more than 20 cigarettes per day and are older than 45 years old are considered to be at high risk. That is, the earlier the age of smoking, the longer the number of years of smoking, and the more cigarettes smoked per day, the higher the chance of developing lung cancer.