Some cancers are found to be advanced because they may be asymptomatic or not obvious in the early stage, which can be easily ignored. It is only when the cancer cells have spread that obvious symptoms will appear, and at that time, the cancer is already at an advanced stage when you seek medical examination. It is generally difficult to detect cancer in the early stage during regular medical checkups, which is why some people still have advanced cancer during annual medical checkups. For example, chest X-ray in medical checkups cannot accurately diagnose early lung cancer, and CT chest examination is generally required for lung cancer screening. Therefore, it is more crucial to prevent cancer, especially those with family history of cancer (cancer often has family aggregation and genetic susceptibility, and those with family history have higher chances of cancer than the general population), precancerous lesions and people over forty years old should undergo cancer screening suitable for themselves every six months or once a year to achieve early detection and early treatment. Meanwhile, if you have long-term cough and abnormal stools, you should not ignore them and seek medical advice to clarify the causes. In addition, factors such as smoking, drinking, staying up late, lack of exercise and unhealthy eating habits can increase the risk of cancer. Therefore, maintaining good living and eating habits can also help prevent cancer. For example, people who smoke should quit smoking as early as possible, and also pay attention to avoid inhaling frying fumes and other harmful gases, which is more crucial to prevent lung cancer.